From The Collaborative International Dictionary of English v.0.48 :
Catchfly \Catch"fly\, n. (Bot.)
A plant with the joints of the stem, and sometimes other
parts, covered with a viscid secretion to which small insects
adhere. The species of Silene are examples of the catchfly.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
catchfly
n 1: any plant of the genus Silene [syn: silene, campion,
catchfly]
2: mostly perennial herbs with sticky stems that catch insects;
widespread in north temperate zone [syn: lychnis,
catchfly]