The Collaborative International Dictionary of English v.0.48:
Thyrse \Thyrse\ (th[~e]rs), n. [Cf. F. thyrse.] A thyrsus. [1913 Webster] ThyrsoidWordNet (r) 3.0 (2006):
thyrse n 1: a dense flower cluster (as of the lilac or horse chestnut) in which the main axis is racemose and the branches are cymose [syn: thyrse, thyrsus]