She began muttering, — "The flame flickers in the eye; the eye shines like dew; it looks soft and full of feeling; it smiles at my jargon: it is susceptible; impression follows impression through its clear sphere; where it ceases to smile, it is sad; an unconscious lassitude weighs on the lid: that signifies melancholy resulting from loneliness.
There are no more uses of "lassitude" in the book.
Show samples from other sources
They did not go hunting at all that night, but stayed near the den and rested, The next morning dawned fine and warm, and a general air of contented lassitude seemed to overcome all three.
Farley Mowat -- Never Cry Wolf
In every sense of the word having experienced rebirth, she possessed some of the lassitude and, as a matter of fact, a great deal of the helplessness of a newborn child.