ACK

ACK as an abbreviation that may refer to:

• Acknowledgement (data networks), a signal to acknowledge the receipt of data
• ACK, a flag used in the Transmission Control Protocol (TCP) to acknowledge receipt of a packet
• Acknowledge character, a control character used in ASCII
• Acklington railway station, a rail station in the United Kingdom
• Amar Chitra Katha, an Indian comic book series
• Amsterdam Compiler Kit, a fast, lightweight and retargetable compiler suite
• Anglican Church of Kenya
• Nantucket Memorial Airport, a Massachusetts airport
• ACK Air, a term commonly used to refer to Nantucket Airlines

Ack as a word may also refer to:

• "Ack ack", from signalese for AA, referring to a term for anti-aircraft artillery fire
• Armstrong Whitworth F.K.8, an early aircraft known as the "Big Ack"
• ack, a command-line utility similar to grep that uses the more extensive Perl regular expressions
• short for "Acknowledgement" (sometimes in the sense of acceptance) in online chat slang