Plausible but untrue

• Plausible but wrong
• Apparently right, but not really so
• Deceptively pleasing
• Convincing at first, but flawed
• False

Longman Dictionary of Contemporary English Word definitions in Longman Dictionary of Contemporary English
adjective EXAMPLES FROM OTHER ENTRIES ▪ specious logic EXAMPLES FROM CORPUS ▪ All that is needed is a positive approach and an end to the specious fear of isolation. ▪ Even so, the size-and-weight-of-head argument is a rather specious one. ▪ In the history ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
late 14c., "pleasing to the sight, fair," from Latin speciosus "good-looking, beautiful, fair," also "showy, pretended, plausible, specious," from species "appearance, form, figure, beauty" (see species ). Meaning "seemingly desirable, reasonable or probable, ...

Wiktionary Word definitions in Wiktionary
a. 1 Seemingly reasoned, plausible or true, but actually fallacious. 2 Having an attractive appearance intended to generate a favorable response; deceptively attractive. 3 (context obsolete English) beautiful, pleasing to look at.

Wikipedia Word definitions in Wikipedia