spe·cious 
(spēshəs)
(spēshəs)adj.
1. Having the ring of truth or plausibility but actually fallacious: a specious argument.
2. Deceptively appealing: "It is easy enough to give the old idea [of programmatic music] a specious air of modernity" (Aaron Copland).
[Middle English, attractive, from Latin speciōsus, from speciēs, appearance; see spek- in the Appendix of Indo-European roots.]
specious·ly adv.
spe′ci·osi·ty (-shē-ŏsĭ-tē), specious·ness (-shəs-nĭs) n.