(cryptography) An attack on a cryptosystem that relies only on the attacker's knowledge of some ciphertexts encrypted with that system and key. Less powerful than a known-plaintext attack.

(cryptography) An attack on a cryptosystem that relies on the attacker's knowledge of not just some ciphertexts encrypted with that system and key, but also their corresponding plaintexts (cribs). More powerful than a ciphertext-only attack, but less powerful than a chosen-plaintext attack.

Alternative form of second preimage attack

(immunology) A formation of transmembrane channels on the surface of a pathogenic bacterial cell that disrupts the phospholipid bilayer of the target cell resulting in its destruction.

In a battle or dispute, attacking the opposition first is better than waiting for them to attack.

plural of complement membrane attack complex

Alternative spelling of attack is the best form of defence

(Canada, informal, education, derogatory) Standardized tests conducted by the Education Quality and Accountability Office in the province of Ontario.