Having the ring of truth or plausibility but actually fallacious: a specious argument.
Deceptively attractive.
[Middle English, attractive, from Latin speciōsus, from speciēs, appearance; see spek- in Indo-European roots.] spe'cious·ly adv., spe'ci·os'i·ty (-shē-ŏs'ĭ-tē), spe'cious·ness (-shəs-nĭs) n.