Meanings

low-level clouds

underground resistance (in wartime)

lower abdominal pain

low-grade fish

Shimose powder (explosive composed chiefly of picric acid)

no more, no less

bottom of the (batting) order

upper and lower houses of parliament

Their Majesties the Emperor and Empress

underpass

downbeat

low-class language

bottom alignment (esp. in a spreadsheet)

fallout (e.g. radioactive)

diarrhea

same as above

company town

(very) watery diarrhea

under ... circumstances

connection to public sewerage