Definition of cracks:
(v) :
(intransitive) To form cracks.
(v) :
(intransitive) To break apart under force, stress, or pressure.
(v) :
(intransitive) To become debilitated by psychological pressure.
(v) :
(intransitive) To break down or yield, especially under interrogation or torture.
(v) :
(intransitive) To make a cracking sound.
(v) :
(intransitive, of a voice) To change rapidly in register.