The Collaborative International Dictionary of English v.0.48:
Lasso \Lass"o\ (l[a^]s"s[-o]) n.; pl. Lassos (-s[=o]z). [Sp.
lazo, L. laqueus. See Lace.]
A rope or long thong of leather with a running noose, used
for catching horses, cattle, etc.
Lasso cell (Zool.), one of a peculiar kind of defensive and
offensive stinging cells, found in great numbers in all
c[oe]lenterates, and in a few animals of other groups.
They are most highly developed in the tentacles of
jellyfishes, hydroids, and Actini[ae]. Each of these cells
is filled with, fluid, and contains a long, slender, often
barbed, hollow thread coiled up within it. When the cell
contracts the thread is quickly ejected, being at the same
time turned inside out. The thread is able to penetrate
the flesh of various small, soft-bodied animals, and
carries a subtle poison by which they are speedily
paralyzed and killed. The threads, at the same time, hold
the prey in position, attached to the tentacles. Some of
the jellyfishes, as the Portuguese man-of-war, and
Cyanea, are able to penetrate the human skin, and
inflict painful stings in the same way. Called also
nettling cell, cnida, cnidocell.