Verb (used without object) : Business is slacking up.    From Dictionary.com. 

Verb (used with object) : He slacked the most important part.    From Dictionary.com. 

Noun : a sudden slack in output.    From Dictionary.com. 

Adjective : a slack rope. ,slack proofreading. ,He is slack in answering letters. ,the slack season in an industry.    From Dictionary.com. 

"How do you like Criterion's paces?" he said, after they had entered the park and were slacking from a canter to a walk.    From Wordnik.com.  [Daniel Deronda] Reference

(And here, I thought we had been slacking, that is, until yesterday when we ran about like freaks to get the place cleaned up ….).    From Wordnik.com.  [Tigers & Strawberries » Bison, Part II] Reference

We guess Philip Roth is kind of slacking in that regard.    From Wordnik.com.  [All Stories | The New York Observer] Reference

If everyone is "slacking", then first of all it's at least fair.    From Wordnik.com.  [The Barefoot Bum] Reference

NATO countries "slacking" in their commitments, including avoidance of actual combat.    From Wordnik.com.  [ThreatsWatch] Reference

I feel like I owe you all a damned fine post because I've been kind of slacking off a bit lately.    From Wordnik.com.  [Progressive Bloggers] Reference

I feel like I owe you all a damned fine post because I’ve been kind of slacking off a bit lately.    From Wordnik.com.  [November « 2008 « knitnut.net] Reference

What about the honeybee slacking off, we're hearing?.    From Wordnik.com.  [CNN Transcript Mar 29, 2007] Reference

So the multitasking actually becomes multi-slacking.    From Wordnik.com.  [CNN Transcript Dec 18, 2004] Reference

Hope you weren't slacking at work on the 360 Web site.    From Wordnik.com.  [CNN Transcript Apr 12, 2008] Reference

And there'd be no slacking in those other areas, either.    From Wordnik.com.  [The Weakling] Reference

Also, the winds are slacking, and so is the storm surge.    From Wordnik.com.  [CNN Transcript Sep 1, 2008] Reference

After Brown left the auto there was no slacking of its speed.    From Wordnik.com.  [Watch Yourself Go By] Reference

COOPER: You've really been slacking off the last couple of years.    From Wordnik.com.  [CNN Transcript Mar 15, 2002] Reference

We went careening along hill-sides without even slacking the trot.    From Wordnik.com.  [Letters of a Woman Homesteader] Reference

See why slacking off in college just may be a successful strategy.    From Wordnik.com.  [CNN Transcript Aug 5, 2006] Reference

The train was slacking up as it steamed into the big, arched station.    From Wordnik.com.  [Dorothy Dale's Queer Holidays] Reference

It's been slacking off the last couple of hours, so it's not pouring.    From Wordnik.com.  [CNN Transcript Feb 22, 2003] Reference

Multi-slacking is someone who slacks at multiple things at the same time.    From Wordnik.com.  [CNN Transcript Oct 13, 2007] Reference

The rain is actually slacking off quite a bit in the last 30 minutes or so.    From Wordnik.com.  [CNN Transcript Sep 5, 2004] Reference

Those of you who have been slacking on running, you're only hurting yourself.    From Wordnik.com.  [CNN Transcript Sep 27, 2007] Reference

The horse was slacking speed a bit now, for the pace was telling on his wind.    From Wordnik.com.  [Tom Swift and His Motor-Cycle, or, Fun and Adventures on the Road] Reference

Those of you that have been slacking on running, you're only hurting yourself.    From Wordnik.com.  [CNN Transcript Oct 2, 2007] Reference

Those of you who have been slacking on running, you're only hurting yourselves.    From Wordnik.com.  [CNN Transcript Sep 25, 2007] Reference

Those of you who have been slacking on running, you ` re only hurting yourselves.    From Wordnik.com.  [CNN Transcript Sep 27, 2007] Reference

All at once there came a sudden slacking of the pull from whatever was in the water.    From Wordnik.com.  [Five Thousand Miles Underground Or, the Mystery of the Centre of the Earth] Reference

CALDWELL: And the guys are slacking, because there was three guys in the bottom three.    From Wordnik.com.  [CNN Transcript Mar 15, 2007] Reference

GARCIA: It was really what allowed the greatest advances in slacking off to take place.    From Wordnik.com.  [CNN Transcript Aug 11, 2006] Reference

At times the rain has been coming down heavily and then slacking off just a little bit.    From Wordnik.com.  [CNN Transcript Jun 12, 2006] Reference

Retail sales falling since Thanksgiving and industrial production has been slacking off.    From Wordnik.com.  [CNN Transcript Apr 5, 2008] Reference

And then, do you know what your teens are doing when they're marinating or multi-slacking?.    From Wordnik.com.  [CNN Transcript Oct 13, 2007] Reference

No one can accuse the increasingly hyphenated comedienne-actress-musician of slacking off.    From Wordnik.com.  [Lee Stranahan: Margaret Cho Talks About New Album, Gay Rights & Head Lice] Reference

"We're going a bit faster!" called Mr. Damon 'encouragingly, "or else they're slacking up.".    From Wordnik.com.  [Tom Swift and His Motor-Boat, or, the Rivals of Lake Carlopa] Reference

"If somebody's slacking they'll get you out of here; that's what Coach Shanahan's here for.".    From Wordnik.com.  [Kyle Shanahan is a young offensive coordinator] Reference

"You tend to overwork as a remote worker because you don't want to appear to be slacking off.".    From Wordnik.com.  [The rise of home working] Reference

Having children is a joy, but it ` s a responsibility, and too many of us are just slacking off.    From Wordnik.com.  [CNN Transcript Oct 3, 2006] Reference

Those of you who have been slacking on running, you're only hurting yourselves, remember that, OK?.    From Wordnik.com.  [CNN Transcript Sep 27, 2007] Reference