Aril \Ar"il\, ||Arillus \A*ril"lus\, n. [From LL. arilli dry grapes, perh. fr. L. aridus dry: cf. F,. arille.] (Bot.) A exterior covering, forming a false coat or appendage to a seed, as the loose, transparent bag inclosing the seed of the white water lily. The mace of the nutmeg is also an aril. --Gray. [1913 Webster]