To hesitate or be unwilling to accept an idea or undertaking. She balked at the high price of the concert tickets.
To stop short and refuse to proceed. The horse balked at the jump, refusing to go over it.
To thwart or hinder a plan or person. The sudden rainstorm balked their plans for a picnic.
In baseball, to commit an illegal motion as a pitcher, allowing base runners to advance. The pitcher balked twice in the ninth inning, moving both runners into scoring position.