balk
/ˈbȯk/
verb
to refuse abruptly —used with at
to stop short and refuse to proceed
to commit a balk
noun
an occurrence in which a pitcher stops suddenly or makes an illegal movement after starting to throw a pitch
failure of a competitor to complete a motion (such as a jump, vault, or dive)
the space behind the balkline on a billiard table
The pitcher was charged with a balk.