n. 1 the act or an instance of forming; the process of being formed. 2 a thing formed. 3 a structure or arrangement of parts. 4 a particular arrangement, e.g. of troops, aircraft in flight, etc. 5 Geol. an assemblage of rocks or series of strata having some common characteristic. formational adj.
[ ME f. OF formation or L formatio (as FORM) ]