The Collaborative International Dictionary of English v.0.48:

Tress \Tress\, n. [OE. tresse, OF. trece, F. tresse, LL. tricia,
   fr. Gr. tri`cha threefold, because a tress is usually formed
   by interlacing three pieces; akin to trei^s three. See
   Three.]
   1. A braid, knot, or curl, of hair; a ringlet.
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            Her yellow hair was braided in a tress. --Chaucer.
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            Fair tresses man's imperial race insnare. --Pope.
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   2. Fig.: A knot or festoon, as of flowers. --Keats.
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WordNet (r) 3.0 (2006):

tress
    n 1: a hairdo formed by braiding or twisting the hair [syn:
         braid, plait, tress, twist]