adj

• (archaic, of force, strength, etc.) Full, sheer, undivided.
  "[…] I shall never forget the diabolical sneer which writhed Rashleigh's wayward features, as I was forced from the apartment by the main strength of two of these youthful Titans."
• (dialectal) Big; angry.
• (nautical) Belonging to or connected with the principal mast in a vessel.
• (obsolete) Great in size or degree; important, powerful, strong, vast.
  "And now that Current with main Fury ran / (The Stop remov'd that did the Courſe defend) / Unto the full of Miſchief, that began / T' an univerſal Ruin to extend; […]"

adv

• (British, dialectal) Exceedingly, extremely, greatly, mightily, very, very much.
  "Suck[y]. A Draught of Ale, Friend, for I'm main dry. / Pen[elope]. Fie! fie! Niece! Is that Liquor for a young Lady? Don't disparage your Family and Breeding!"

verb

• (transitive, slang) Ellipsis of mainline (“to inject (a drug) directly into a vein”).
• (transitive, gaming) To mainly play a specific character or side, or with specific equipment, during a game.
  "He mains the same character as me in that game."
• (obsolete) To convert (a road) into a main or primary road.
  "When a rural district council considers that a highway in its district ought to become a main road by reason of its being a medium of communication between great towns, or a thoroughfare to a railway station, or otherwise, it may apply to the county council for an order "maining" the road under s. 15 of the Highways and Locomotives (Amendment) Act, 1878 (41 & 42 Vict. c. 77), as amended by s. 3 (viii.) of the Local Government Act, 1888 (51 & 52 Vict. c. 41), and the county council may make an order accordingly."

noun

• (not in generic modern use) That which is chief or principal; the chief or main portion; the bulk, the greater part, gross.
  "Antiochus […] thought it a proper time for him to attempt the recovery of Syria; and Hermias his prime Miniſter preſſed hard for his going in perſon to this war, contrary to the Opinion of Epigenes his General; who thought it chiefly concerned him to ſuppreſs the Rebellion of Alexander and Molon in the East; and therefore adviſed him to march immediately in perſon with the main of his Army for the ſubduing of thoſe Rebels, before they ſhould gather greater ſtrength in the revolted Provinces againſt him."
• (not in generic modern use) That which is chief or principal; the chief or main portion; the bulk, the greater part, gross.
  "My WoW main has reached level cap and I’m on my way getting my first alt there as well."
• (not in generic modern use) That which is chief or principal; the chief or main portion; the bulk, the greater part, gross.
  "His main got banned after his last post."
• (informal) Ellipsis of main course (“the principal dish of a meal”).
  "I had scampi and chips for my main and a slice of cheesecake for dessert."