Achillean :: Achillean (a.) Resembling Achilles, the hero of the Iliad; invincible..
Achilles' Tendon :: Achilles' tendon (n.) The strong tendon formed of the united tendons of the large muscles in the calf of the leg, an inserted into the bone of the heel; -- so called from the mythological account of Achilles being held by the heel when dipped in the River Styx..
Acquaintanceship :: Acquaintanceship (n.) A state of being acquainted; acquaintance.
Acrolithic :: Acrolithic (a.) Pertaining to, or like, an acrolith..
Adelphia :: Adelphia (n.) A brotherhood, or collection of stamens in a bundle; -- used in composition, as in the class names, Monadelphia, Diadelphia, etc..