At breakneck speed is a phrase used to describe an action that is done very quickly and with great urgency. The crossword solutions for this phrase are RAPID (5 letters), HEADLONG (8 letters), and HECTIC (6 letters). RAPID means moving or occurring with great speed, HEADLONG means done with great haste and without thought or caution, and HECTIC means characterized by intense activity and agitation. All three words accurately describe the phrase at breakneck speed.