Antiaircraft artillery. / (uncountable) Antiaircraft fire.

plural of ack-ack

(networking) An acknowledgement either of a packet or a message received from a network.

(networking) To acknowledge a packet or a message received from a network.

(military, now historical) The letter A as used in signalling and other types of communications. / (data communications) acknowledgment signal

Alternative form of ACK.

(radio communications) acknowledged

Expressing distaste, alarm, or trepidation.

plural of ack

plural of ACK