CIDE DICTIONARY
seldom, adv. [AS. seldan, seldon, seldum, fr. seld rare; akin to OFries. sielden, D. zelden, G. selten, OHG. seltan, Icel. sjaldan, Dan. sielden, Sw. sällan, Goth. sildaleiks marvelous.].
THESAURUS
seldom
abnormally, at infrequent intervals, few, hardly, hardly ever, incredibly, infrequently, irregularly, little, not often, occasional, occasionally, rare, rarely, scarce, scarcely, scarcely ever,
seldom if ever, sparsely, sporadic, sporadically, uncommon, uncommonly, uncustomarily, unexpectedly, unfrequent, unfrequently, unnaturally, unoften, unordinarily, unusually, very
seldom
ROGET THESAURUS
seldom
Infrequency
N
infrequency, rareness, rarity, fewness, seldomness, uncommonness, unfrequent, infrequent, rare, rare as a blue diamond, few, scarce, almost unheard of, unprecedented, which has not occurred within the memory of the ol, not within one's previous experience, not since Adam, scarce as hen's teeth, one in a million, few and far between,
seldom, rarely, scarcely, hardly, not often, not much, infrequently, unfrequently, unoften, scarcely, scarcely ever, hardly ever, once in a blue moon, once, once in a blue moon, once in a million years, once for all, once in a way, pro hac vice, ein mal kein mal.