na-adjective
bored-looking; uninterested; seeming bored
Describes someone who appears bored or uninterested. Often used to describe a person's expression or attitude. The form is the そう (hearsay/appearance) of つまらない, but with the irregular stem つまらなさ.
See also: 詰まらなそう
彼はつまらなさそうに窓の外を見ていた。
He was looking out the window with a bored expression.
その映画はつまらなさそうだったので、見なかった。
The movie looked boring, so I didn't watch it.