Here's how it works:
* Trumpet: A musical instrument known for its loud and proud sound.
* Blow: To play the trumpet.
* One's own: Referring to oneself.
The phrase implies that someone is making a lot of noise about their own accomplishments, much like a trumpet player might loudly announce their presence with a fanfare.
Example:
"John kept blowing his own trumpet about his promotion, which annoyed his colleagues."
Similar expressions:
* Toot one's own horn
* Brag
* Show off
Note: The expression is usually used in a negative context, implying that someone is being arrogant or self-important.