What does arms mean?
The definition of arms
Arms, n. pl.
Etym: [OE. armes, F. arme, pl. armes, fr. L. arma, pl., arms, orig. fittings, akin to armus shoulder, and E. arm. See Arm, n.]

1 Instruments or weapons of offense or defense. He lays down his arms, but not his wiles. Milton. Three horses and three goodly suits of arms. Tennyson.
2 The deeds or exploits of war; military service or science. “Arms and the man I sing.” Dryden.
3 (Law)
Anything which a man takes in his hand in anger, to strike or assault another with; an aggressive weapon. Cowell. Blackstone.
4 (Her.)
The ensigns armorial of a family, consisting of figures and colors borne in shields, banners, etc., as marks of dignity and distinction, and descending from father to son.
5 (Falconry)
The legs of a hawk from the thigh to the foot. Halliwell. Bred to arms, educated to the profession of a soldier.

— In arms, armed for war; in a state of hostility.
— Small arms, portable firearms known as muskets, rifles, carbines, pistols, etc.
— A stand of arms, a complete set for one soldier, as a musket, bayonet, cartridge box and belt; frequently, the musket and bayonet alone.
— To arms! a summons to war or battle.
— Under arms, armed and equipped and in readiness for battle, or for a military parade. Arm’s end, Arm’s length, Arm’s reach. See under Arm.