n. 1 the act or an instance of extending; the process of being extended. 2 prolongation; enlargement. 3 a part enlarging or added on to a main structure or building. 4 an additional part of anything. 5 a a subsidiary telephone on the same line as the main one. b its number. 6 a an additional period of time, esp. extending allowance for a project etc. b permission for the sale of alcoholic drinks until later than usual, granted to licensed premises on special occasions. 7 extramural instruction by a university or college (extension course). 8 extent, range. 9 Logic a group of things denoted by a term. extensional adj.
[ ME f. LL extensio (as EXTEND) ]