The relentlessness or their pursuit.    From Wordnet, Princeton University. 

Caroline: Yes, very insightful, "relentlessness" - is the word I would have used if I could have thought of it.    From Wordnik.com.  [BP and brain problems: "Help, I've fallen and I can't get up!"] Reference

Sally had a kind of relentlessness to her, and I say that and it sounds like it could be a negative thing.    From Wordnik.com.  [StarTribune.com rss feed] Reference

He put his running success down to "relentlessness" and said he felt good after the seven-and-a-half week challenge.    From Wordnik.com. Reference

Izzard put his running success down to "relentlessness" and said he felt good after the seven-and-a-half week challenge.    From Wordnik.com. Reference

"relentlessness" of the campaign had led to the loss of a great head-teacher.    From Wordnik.com.  [Kos RSS Feed] Reference

Because I like Brent's relentlessness, five goats.    From Wordnik.com.  [James Frey: Store-Openings and Surprises on The Fabulous Beekman Boys Season Finale] Reference

And some are just worn down by Fuller's relentlessness.    From Wordnik.com.  [A New Guilty Pleasure] Reference

Burke confronted Jacobinism with the relentlessness of a.    From Wordnik.com.  [Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary"] Reference

And if there's one hallmark of Al Gore, it is relentlessness.    From Wordnik.com.  [CNN Transcript - Larry King Live: Peter Jennings Discusses 'Family Business' - September 14, 2000] Reference

They just don't possess the relentlessness that makes it possible.    From Wordnik.com.  [Antonio Garcia-Martinez: Startup Founders And F*ck You, Money] Reference

With the relentlessness of Greek tragedy, destiny takes its course.    From Wordnik.com.  [Maigret Hesitates]

It indicates the wonderful relentlessness of trying to make it smarter and better.    From Wordnik.com.  [Q&A: Fringe’s Blair Brown: Adam Klappholz] Reference

The Greek Fates were pictured as moving with just that even relentlessness of stride.    From Wordnik.com.  [Montlivet] Reference

At Louvain, at Brussels, he gave fresh examples of his relentlessness as an overlord.    From Wordnik.com.  [Charles the Bold Last Duke of Burgundy, 1433-1477] Reference

Their relentlessness generated media attention, which further fueled their dedication.    From Wordnik.com.  [Dan Brown: Illuminating Public Schools' Possibilities: "Spectacular Things Happen Along the Way"] Reference

He knew their relentlessness in the chase; and he must be free in order to redeem himself.    From Wordnik.com.  [The Return of Blue Pete] Reference

Her first interview with Sobrenski had shown the relentlessness of the man she was to serve.    From Wordnik.com.  [The Hippodrome] Reference

I think my heritage and my relentlessness does more than because my crimes were 30 years ago.    From Wordnik.com.  [CNN Transcript Nov 30, 2009] Reference

The unprecedented relentlessness of Romney's flip-flopping is his campaign's biggest problem.    From Wordnik.com.  [Lawrence O'Donnell: Romney & Me] Reference

The relentlessness of media-driven pop culture deadens our senses to authentic truth, beauty, and wisdom.    From Wordnik.com.  [Jennifer Nix: Crunchy Cons, Obama and Election 2008] Reference

Romney, who dislikes running even a minute late, will bring the same relentlessness to his campaign operation.    From Wordnik.com.  [Governor Romney, Meet Governor Romney] Reference

But the Lombards threw into their work their own restless energy, and some of their cruelty and relentlessness.    From Wordnik.com.  [Arts and Crafts in the Middle Ages A Description of Mediaeval Workmanship in Several of the Departments of Applied Art, Together with Some Account of Special Artisans in the Early Renaissance] Reference

It takes in the mysteries of male friendship, the relentlessness of grief and the lure of emotional parasitism.    From Wordnik.com.  [The Finkler Question by Howard Jacobson] Reference

I have to congratulate the Hillary-bashers for their relentlessness in the face of all evidence to the contrary.    From Wordnik.com.  [In New Hampshire, Hillary Pulls Away From Obama] Reference

During her entire presidential campaign, she exhibited "tenacity" and a "relentlessness and refusal to say die.".    From Wordnik.com.  [Kevin Morris and Glenn Altschuler: The End of Politigation] Reference

But I was probably naive not to have expected the relentlessness of the diatribe I faced throughout the segment.    From Wordnik.com.  [Robert H. Frank: Success and Luck] Reference

But besides the hypocrisy, the scariness of her relentlessness was truly brought home to me tonight by Rachel Maddow.    From Wordnik.com.  [Hillary's Hypocrisy] Reference

Except for the aura of money and the manufactured air of relentlessness, there seems less and less substance in her campaign.    From Wordnik.com.  [Poll: Obama Creeping Up On Hillary; Rudy's Lead Grows] Reference

His relentlessness, coupled with the power of his office, was just enough for him to win most of the right over, however grudgingly.    From Wordnik.com.  [President McCain and the Soul of the Republican Party] Reference

Nxesi told the council teachers 'relentlessness commitment to reduce gender, knowledge and wealth gaps could not be over emphasised.    From Wordnik.com.  [ANC Daily News Briefing] Reference

If they're not saying it with sufficient force or passion or relentlessness to get the message in the MSM, than that's their failure too.    From Wordnik.com.  [Iraq and the Defense Bill: A Post-Mortem Guide for the Perplexed] Reference

"What are you going to do about it?" he continued with the relentlessness of a man who likes a prompt decision, even if it be a wrong one.    From Wordnik.com.  [Defenders of Democracy; contributions from representative men and women of letters and other arts from our allies and our own country, edited by the Gift book committee of the Militia of Mercy] Reference