lissom
Flexible and graceful in movement; lithe.
Now, our country lads, [...] are so much better made, so much more athletic, and yet so much lissomer—to use a Hampshire phrase, which deserves at least to be good English.
Where it comes from
From Middle English lithsum, equivalent to lithe + -some. Doublet of lithesome.
Adapted from the Wiktionary entry lissom (CC BY-SA 4.0).