(nautical) On a wooden mast, a circular disc (or sometimes a rectangle) of wood near or at the top of the mast, usually with holes or sheaves to reeve signal halyards; also a temporary or emergency place for a lookout.

With all one's strength; as hard as one can.

All one's strength.

plural of main wheel

Any of the main wheels of a device (such as an aircraft or wheelchair) that has multiple wheels.

Alternative spelling of mainmast

(US, slang) The primary woman that a man is romantically involved with / (by extension) Something or someone of great importance.

The most important factor; the principle consideration.

A general contractor.

plural of main contractor.