1. klaxon - Noun
2. klaxon - Verb
a kind of loud horn formerly used on motor vehicles
Source: WordNetThese sirens, mostly built by Carter, Gents Tangent, Castle Castings, and Klaxon Signal Co., have 10 and 12 ports to create a minor third interval (B and D notes) and are probably the world's most recognized World War II air-raid siren sound. Source: Internet