(1) (being located) Between or among cells.
(2) Of or pertaining to that (e.g. substance, space, region) between the cells.
For instance, intercellular fluid refers to the fluid between cells.
Word origin: from Middle English entre-, inter-, from Old French entre-, from Latin inter-, from inter (between, among) + cellular from Latin cellulāris, equivalent to cellul(a) (live cell).