We found one dictionary that defines the word ack-ack guns:

General (1 matching dictionary)

1. ack-ack guns, ack-ack guns: Collins English Dictionary

(Note: See ack-ack_gun as well.)

Definitions from WordNet (ack-ack gun) ▸ noun:  artillery designed to shoot upward at airplanes ▸ Also see ack-ack_gun ▸ Words similar to ack-ack guns ▸ Usage examples for ack-ack guns ▸ Idioms related to ack-ack guns ▸ Wikipedia articles (New!) ▸ Words that often appear near ack-ack guns ▸ Rhymes of ack-ack guns ▸ Invented words related to ack-ack guns