striation (stri-a'-tion). (a) stria. (b) One of multiple scratches or minute lines, generally parallel, inscribed on a rock surface by a geologic agent, e.g., glaciers ( glacial striation ), streams (cf: drag mark ), or faulting (cf: slickenside ). Syn: scratch. (c) The condition of being striated; the disposition of striations. Adj: striated; striate.