Source : Webster's Revised Unabridged Dictionary (1913)

Tam-o'-shanter \Tam`-o'-shan"ter\, n. [So named after Tam
   o'Shanter, a character in Burns's poem of the same name.]
   A kind of Scotch cap of wool, worsted, or the like, having a
   round, flattish top much wider than the band which fits the
   head, and usually having a tassel in the center.

Source : WordNet®

tam-o'-shanter
     n : a woolen cap of Scottish origin [syn: {tam}, {tammy}]