To make something neat or of the required size or form by cutting away irregular or unwanted parts. She decided to trim the hedge to keep it looking tidy.
To reduce the size, amount, or number of something. The company had to trim its budget to stay profitable.
To decorate or add ornaments to something. They trimmed the Christmas tree with lights and tinsel.
To adjust a vessel's sails or an aircraft's control surfaces so that it maintains the desired balance or course. The pilot trimmed the aircraft for level flight before engaging the autopilot.