inane

in|ane /ɪn'eɪn/
[ADJ]
If you describe someone's behaviour or actions as inane, you think they are very silly or stupid.
He always had this inane grin...
= idiotic
● inanely [ADV] ADV after v
He lurched through the bar, grinning inanely.
● inanity [N-UNCOUNT]
...the inanity of the conversation.