Origin: 1535–45; < L
plausibilis deserving applause, equiv. to
plaus(
us) (ptp. of
plaudere to
applaud ) +
-ibilis -ible 
Related forms: plau⋅si⋅bil⋅i⋅ty, plau⋅si⋅ble⋅ness, noun
plau⋅si⋅bly, adverb
Synonyms:
1. Plausible, specious describe that which has the appearance of truth but might be deceptive. The person or thing that is plausible strikes the superficial judgment favorably; it may or may not be true: a plausible argument (one that cannot be verified or believed in entirely). Specious definitely implies deceit or falsehood; the surface appearances are quite different from what is beneath: a specious pretense of honesty; a specious argument (one deliberately deceptive, probably for selfish or evil purposes).
Antonyms:
1. honest, sincere.