Verb (used without object) : He balked at making the speech.    From Dictionary.com. 

Verb (used with object) : a sudden reversal that balked her hopes. ,to balk an opportunity.    From Dictionary.com. 

Noun : to make a balk.    From Dictionary.com. 

"Which, while they're still fast friends, was the last word ever passed between them on the subject of the funker and the balker.".    From Wordnik.com.  [The Red-Blooded Heroes of the Frontier] Reference

"'Yes,' I said, 'an' I've knowed better judges of hosses to sell a nervous hoss for a balker that had been balked onct by a rattle head.    From Wordnik.com.  [The Bishop of Cottontown A Story of the Southern Cotton Mills] Reference