(1) Of or pertaining to a tissue that is not made of cells or not divided into cells, such as hyphae of some fungi.
(2) Noncellular; a living entity without cell(s), as in the Mimivirus, viroids, prions, satellites, plasmids, etc.
(3) Not containing any cells, as in acellular vaccine.
(4) Unicellular; pertains to single-celled organisms, such as protozoans and ciliates.
Word origin: prefix meaning "not," from Gk. a-, an- "not," + NL cellulāris, equiv. to cellul(a) live cell (L: little room).
Related phrases: acellular vaccine.
See also: cells, tissues.