1) To adjust the set of the sails to best advantage.

Trim, to (2) To adjust the sit of a boat in the water to the best advantage, usually so that she floats parallel to the designed waterline, though there may be times when it is desired to trim a boat by the head (bow down) or by the stern (bows up) for some special purpose. In a rowing boat, the request ‘trim the boat’ requires the passengers to shift their weight so that the boat will be level. The verb may also be intransitive, as they say at school, for the boat herself may be observed to ‘trim by the head’, for example.