Intrude, join without being invited. For example, She has a rude way of horning in on our conversations. This expression alludes to an ox or bull pushing in with its horns. [c. 1900]
Thou shalt not horn in on thy husbands racket Homer
Some beginners start on another type Single B flat horn
animal a) [countable] the hard pointed thing that grows, usually in pairs, on the heads of animals such as cows and goats → antlers b) [uncountable] the
Golden french horn in soft light isolated on white background
Liberal Dictionary English Dictionary
