flash, flashing, steal look
闚 centers on a quick, furtive visual act: a flash of a look, a stolen glance, or peeping through a gap. The given meanings all involve brief, often secretive observation.
闚 combines 門 (gate) with 規, which likely contributes the sound and the idea of observing or measuring. The character suggests peeping through a gate or gap.
Through the gate 門, you see a 規 (standard, rule) — imagine stealing a quick look at the rules posted outside, just a flash before you're caught.
For キ, imagine a keyhole in the gate: you flash a look through the keyhole — key -> キ.