[codeonfire]

Generally, the most telltale sign of "not-smart" is someone being easily swayed by emotion or persuasion, gullible, pandering, and full of misplaced idealism or concern. Often not-smart people will exhibit these things and you feel embarrassed for them. Examples are people who fall for stupid sales pitches, executives that fall for buzzword technologies, blatant pandering to an authority, or someone is simply confused by basic conversations.

Some people get good at masking "not-smart" by doing things like repeating back what is said to them as their own idea later in the same conversation (very weird) or attributing their belief to someone else "Bill told us that Microsoft Bob was going to be big, so we installed it on all the systems at our company."