The Collaborative International Dictionary of English v.0.48:
xl \xl\, adj. 1. the Roman number symbolizing the value forty. Syn: forty, 40, twoscore. [WordNet 1.5]WordNet (r) 3.0 (2006):
xl adj 1: being ten more than thirty [syn: forty, 40, xl, twoscore] n 1: the cardinal number that is the product of ten and four [syn: forty, 40, XL]