One who balks; a person or animal that stubbornly refuses to proceed or cooperates, or a pitcher who makes a balk in baseball.
From 'balk' + agent suffix '-er,' creating a noun that identifies someone who performs the action of balking.
In old-time baseball, calling someone a 'balker' was a serious insult—it meant they were a deceptive player who broke the rules on the mound!
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