WordNet sense 1 (having low density):

rarefied, rarified

WordNet sense 2 (relatively thin in consistency or low in density; not viscous):

thin

WordNet sense 3 (beyond what is ordinary or usual; highly unusual or exceptional or remarkable):

extraordinary

WordNet sense 4 (not frequent; not occurring regularly or at short intervals):

infrequent

WordNet sense 5 (not treated with heat to prepare it for eating):

raw

WordNet sense 6 (not common or ordinarily encountered; unusually great in amount or remarkable in character or kind):

uncommon

WordNet sense 7 (deficient in quantity or number compared with the demand):

scarce