Well, "slithy" means "lithe and slimy." "Lithe" is the same as "active." You see it's like a portmanteau - there are two meanings packed up into one word.
Lewis CarrollWhere should I go?" -Alice. "That depends on where you want to end up." - The Cheshire Cat.
Lewis CarrollDo you hear the snow against the windowpanes, Kitty? How nice and soft it sounds! Just as if some one was kissing the window all over outside. I wonder if the snow loves the trees and fields, that it kisses them so gently? And then it covers them up snug, you know, with a white quilt; and perhaps it says, 'Go to sleep, darlings, till the summer comes again.' And when they wake up in the summer, Kitty, they dress themselves all in green, and dance about - whenever the wind blows.
Lewis CarrollLastly, she pictured to herself how this same little sister of hers would, in the after-time, be herself a grown woman; and how she would keep, through all her riper years, the simple and loving heart of her childhood: and how she would gather about her other little children, and make their eyes bright and eager with many a strange tale, perhaps even with the dream of Wonderland of long ago: and how she would feel with all their simple sorrows, and find a pleasure in all their simple joys, remembering her own child-life, and the happy summer days.
Lewis Carroll