Wordnet 3.0
NOUN (1)
1.
the hood or cap covering the calyx of certain plants: e.g., the California poppy;
The Collaborative International Dictionary of English v.0.48:
Calyptra \Ca*lyp"tra\ (k[.a]*l[i^]p"tr[.a]), n. [NL., fr. Gr.
kaly`ptra a covering for the head, fr. kaly`ptein to cover.]
(Bot.)
A little hood or veil, resembling an extinguisher in form and
position, covering each of the small flasklike capsules which
contain the spores of mosses; also, any similar covering
body.
[1913 Webster]
WordNet (r) 3.0 (2006):
calyptra
n 1: the hood or cap covering the calyx of certain plants: e.g.,
the California poppy