English Canada / United States
"ROCK!" (pronounced /rɒk/)
"ROCHE!" (pronounced /ʁɔʃ/)
"CAILLOU !" (pronounced /ka.ju/)
It's French but also sometimes used by non-francophone climbers and hikers in the Alps. This word is used to warn when a hiker (or a goat!) up the trail loosens a rock that crosses the trail lower down. Fun fact: Literally it means pebble.
"STEIN!" (pronounced /ʃtaɪn/)
Used in German speaking regions. Exact pronunciation varies in between regions due to dialects, but should be recognisably similar.
"BELOW!" (pronounced /bɪˈləʊ/)
Used in climbing and in caving; amongst others (e.g. scramblers), knowledge of it is variable.
"STEN!" (pronounced /ste:n/)
Mainly used in climbing and caving.