blos·som / ˈbläsəm/ • n. a flower or a mass of flowers on a tree or bush: tiny white blossoms the slopes were ablaze with almond blossom. ∎  the state or period of flowering: fruit trees in blossom.• v. [intr.] (of a tree or bush) produce flowers or masses of flowers: the mango trees have shed their fruit and blossomed again. ∎  mature or develop in a promising or healthy way: their friendship blossomed into romance. ∎  seem to grow or open like a flower: the smile blossomed on his lips.DERIVATIVES: blos·som·y adj.

blossom flower OE.; mass of flowers on a tree XIII. OE. blōstm, blōs(t)ma corr. to (M)Du. bloesem. MLG. blós(s)em; cf. ON. blómstr; gen. referred to the same base as BLOOM1. viz. *blð-, of which *blðs- appears to be an extended form.
Hence blossom vb. OE. blōstmian. blossomy XIV; see -Y1.