fatuous
adj.
5L fatuus, foolish < IE base *bhat3, to strike > BATTER16
1 complacently stupid or inane; silly; foolish
2 [Archaic] like an ignis fatuus; illusory; unreal

—SYN SILLY
fat$u[ous[ly
adv.
fat$u[ous[ness
n.