Fold1  —v. 1 a bend or close (a flexible thing) over upon itself. B (foll. By back, over, down) bend part of (a thing) (fold down the flap). 2 become or be able to be folded. 3 (foll. By away, up) make compact by folding. 4 (often foll. By up) colloq. Collapse, cease to function. 5 enfold (esp. Fold in the arms or to the breast). 6 (foll. By about, round) clasp (the arms). 7 (foll. By in) mix (an ingredient with others) gently. —n. 1 folding. 2 line made by folding. 3 folded part. 4 hollow among hills. 5 curvature of geological strata.