The Collaborative International Dictionary
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.
Douglas Harper's Etymology Dictionary
c.1840, type of bonnet formerly worn by Scottish plowmen, from Tam O'Shanter "Tom of Shanter," name of hero in a poem of the same name by Robert Burns, written 1790. The woolen cap became fashionable for ladies c.1887.
Wiktionary
n. A traditional Scottish wool hat, with a bobble in the centre.
WordNet
Usage examples of "tam-o'-shanter".
They made a colorful cross-section, many of them wearing the old traditional national costumes that had lain in trunks for generationsembroidered dirndls, elaborate peasant blouses, Balkan tunics, sarongs, chesterfields, tam-o'-shanters, gray flannels, and regimental ties.
I passed the time browsing in the windows of the many tourist shops that stand along it, reflecting on what a lot of things the Scots have given the world - kilts, bagpipes, tam-o'-shanters, tins of oatcakes, bright yellow jumpers with big diamond patterns of the sort favoured by Ronnie Corbett, plaster casts of Greyfriars Bobby looking soulful, sacks of haggis - and how little anyone but a Scot would want them.