gormless
A friend pointed out that gormless seemed to be out of favour, despite being such a satisfactory word. Moreover, it did not seem to have its natural opposite, gormful.
It turns out that gorm is a variant of gaum, a dialectal word that appears in a broad range of Scottish and northern dialects, meaning ‘attention, comprehension’. This word derives from Old Norse. In these dialects gaumless meant ‘wanting in sense’ and gaumish meant ‘clever’. He’s a gaumish sort of chap.
While I agree with my friend that gormless is probably on the way out, if it were to be used, these days the emphasis would be on a lack of initiative or spirit. It is almost the equivalent of spineless. But ‘wanting in sense’ is still there. Who can forget the great gormlessness of Norman Gunston.