crack verb
1 break
ADV. badly The dish had cracked quite badly. | slightly
2 become mentally ill
ADV. completely | finally The stresses of her job became too great and she finally cracked. | up He thought he'd never get through the ordeal without cracking up.
PHRASES crack under the pressure/strain, show signs of cracking He is under a lot of pressure but is showing no signs of cracking. PHRASAL VERBS crack down
ADV. hard
PREP. on to crack down hard on crime