toot
n. countablen. a short, sharp sound made by a horn or a whistle. You might hear this when a car driver wants to get someone's attention.
n. a brief, high-pitched sound produced by a horn, whistle, or similar wind instrument. Often used to describe the sound of a vehicle or a toy.
The driver gave a quick toot on his horn.
We heard a friendly toot from the tugboat as it passed under the bridge.
The silence of the morning was broken by the distant toot of a steam train echoing through the valley.
Probably onomatopoeic in origin. Compare Dutch toeteren (“to blow a horn”), German tuten, Swedish tuta, Danish tude. Noun etymology 1 sense 7 ("Mastodon post") and verb etymology 1 sense 10 ("to post on Mastodon") are influenced by tweet (“Twitter post”).
Perhaps a contraction of toilet.
Often used with the preposition 'on' to specify the instrument producing the sound.