Balk also Baulk (verb)
balk
to stop, as at an obstacle, and refuse to proceed or to do something specified / (of a horse, mule, etc.) to stop short and stubbornly refuse to go on.
First recorded before 900; Middle English; Old English balca “covering, beam, ridge”; cognate with Old Norse bǫlkr “bar, partition,” Dutch balk, Old Saxon balko, German Balken, Old Norse bjalki “beam,” Old English bolca “plank”
Example sentences
“I saw him balk at the idea the moment it was mentioned.”