school (e.g. of flower arrangement)

pyroclastic flow

to wash away; to sweep away; to carry away

return current; convection; reflux

alternating current; AC

cancellation

circulation (of money, goods, etc.); distribution

mountain stream; mountain torrent

to forfeit (a pawn)

(the) mainstream

outflow (of people, capital, etc.); drain (of gold, talent, etc. from a country); leak (e.g. of personal information)

upper classes