showing a lack of common sense or sound judgment
‘I am astonished … that you should be so ready to think your own children silly.’ … ‘If my own children are silly, I must hope to be always sensible of it.’ — Jane Austen
trifling or frivolous
a silly remark
stunned or dazed
was scared silly
in cricket, denoting or occupying a fielding position in front of and dangerously near the batsman
silly mid-off
archaic
simple and unsophisticated
Perhaps their loves, or else their sheep, was all that did their silly thoughts so busie keep — Milton
feeble-minded
Davie's no just like other folk … but he's no sae silly as folk tak him for — Scott
sillily adv
silliness noun
Old English sǣlig happy, fortunate, blessed by God, from Old English sǣl happiness. During the Middle English period the word came to mean ‘holy, pious’, hence ‘innocent, harmless, defenceless, pathetic’, also, by the 15th cent. ‘ignorant, simple, foolish’