/fawr"tee/ , n. , pl. forties , adj.
n.
1. a cardinal number, ten times four.
2. a symbol for this number, as 40 or XL or XXXX.
3. a set of this many persons or things.
4. forties , the numbers, years, degrees, or the like, from 40 through 49, as in referring to numbered streets, indicating the years of a lifetime or of a century, or degrees of temperature: His office is in the West Forties. Her parents are in their forties. The temperature will be in the forties.
adj.
5. amounting to 40 in number.
[ bef. 950; ME fourti, OE feowertig (c. OFris fiuwertich, OHG fiorzug, G vierzig ). See FOUR, -TY 1 ]