Definition of XL:
(n) :
(automotive) A designation for a trim level within a model of trucks; it denotes midrange features.
(n) :
(chiefly clothing) Initialism of extra large (the manufactured size or an item of that size). [(uncountable) One of several sizes to which an item may be manufactured.]
(adj) :
(chiefly clothing) Initialism of extra large (of the manufactured size). [(especially clothing) That is extra large (the manufactured size).]