2. Rare; not dense or thick; applied to fluids or soft mixtures; as, thin blood; thin broth; thin air. In the day, when the air is more thin. (bacon) Satan, bowing low His gray dissimulation, disappeared, Into thin air diffused. (milton)
3. Not close; not crowded; not filling the space; not having the individuals of which the thing is composed in a close or compact state; hence, not abundant; as, the trees of a forest are thin; the corn or grass is thin. Ferrara is very large, but extremely thin of people. (Addison)
Origin: OE. Thinne, thenne, thunne, AS. Thynne; akin to D. Dun, G. Dunn, OHG. Dunni, Icel. Thunnr, Sw. Tunn, Dan. Tynd, Gael. & Ir. Tana, W. Teneu, L. Tenuis, Gr. (in comp) stretched out, stretched, stretched out, long, Skr. Tanu thin, slender; also to AS. Enian to extend, G. Dehnen, Icel. Enja, Goth. Anjan (in comp), L. Tendere to stretch, tenere to hold, Gr. To stretch, Skr. Tan. 51 & 237. Cf. Attenuate, Dance, Tempt, Tenable, Tend to move, Tenous, Thunder, Tone.