The Collaborative Dictionary
xiii \xiii\, adj.
the Roman number symbolizing the value thirteen.
Used after a noun it may symbolize the ordinal number; as,
Superbowl XIII. Syn: thirteen,
[WordNet 1.5]
Word Net
xiii adj : being one more than twelve [syn:
thirteen,
13] n : the cardinal
number that is the sum of twelve and one [syn:
thirteen,
13,
baker's
dozen,
long
dozen]