scout, sentinel
哨 centers on watching and guarding: a scout or sentinel who keeps watch, often from a high or forward position.
哨 combines 口 (mouth) with 肖, which likely contributes the sound and may relate to a small or pointed shape, suggesting a person using their mouth to call out while watching.
A mouth 口 beside 肖, which looks like a small pointed watchtower: a sentinel shouting a warning from a high post.
For ショウ, imagine a scout on a showboat keeping watch: show -> ショウ, and the sentinel calls out from the deck.
patrol (with ships or aircraft); patrolling
outpost
sentry; sentinel
shawm-like instrument played by street vendors (sometimes referred to as a flute)
general outpost; GOP
general outpost line
outpost duty
outpost
(preliminary) skirmish
scouting line
outpost cavalry
sentry
suona (Chinese shawm)
Mitella stylosa (species of miterwort)
patrol plane
patrol boat
military patrol boat
sentry post; guard post
sentry box
antisubmarine patrol plane