(nautical) The rope connected to and controlling the mainsail.

A chief support. / Someone or something that can be depended on to make a regular contribution. / (nautical) A stabilising rope from the top of the mainmast to the bottom of the foremast.

plural of mainstay

(nautical) The largest (or only) sail on a sailing vessel.

(horology) The principal spring of a clockwork mechanism, which drives it by uncoiling. / (figuratively) The most important reason for, or element of, something.

plural of mainspring

(geology) The largest earthquake in a sequence, sometimes preceded by foreshocks and almost always followed by aftershocks which are of lesser intensity.

plural of mainsail

simple past tense and past participle of mainstream

Third-person singular simple present indicative form of mainstream