The Collaborative International Dictionary of English v.0.48:
Sneeringly \Sneer"ing*ly\, adv. In a sneering manner. [1913 Webster]WordNet (r) 3.0 (2006):
sneeringly adv 1: with a sneer; in an uncomplimentary sneering manner; "`I don't believe in these customs,' he said sneeringly" [syn: sneeringly, superciliously, snidely]