(botany) A type of inflorescence; a compact panicle having an obscured main axis and cymose subaxes.
1998, D. W. Stevenson, M. Colella, B. Boom, Rapateaceae, Klaus Kubitzki, H. Huber (editors), The Families and Genera of Vascular Plants, Volume IV: Flowering Plants, Monocotyledons: Alismatanae and Commelinanae (except Gramineae), page 417,
The number of spikelets is variable, and some genera have thyrses with 70 spikelets (Saxofridericia, Spathanthus) or only 1-3 spikelets per inflorescence (Stegolepsis, Monotrema).
(archaic) A thyrsus (staff with conical ornament).