To be unwilling to do something or to allow something to happen. (Cambridge Dictionary)
Hesitate or be unwilling to accept an idea or undertaking. (Oxford Dictionaries)
Prevent a person or animal from having (something) (Oxford Dictionaries)
A ridge of land left unplowed as a dividing line or through carelessness. (Merriam – Webster)
If you balk at something, you definitely do not want to do it or to let it happen. (Collins Dictionary)
Why Horses Balk and What to Do About It.
Republicans back Trump on border wall funding, balk at shutdown threats.
What are other words for balk.