In the Second World War (1939–45): a German minesweeper. Now historical.
Origin
1940s; earliest use found in The Times. From R + boat, after German R-Boot, shortened (after U-Boot) from Räumboot minesweeper from räumen to clear, clear away + Boot.
Definition of R-boat in US English:
R-boat
nounˈɑːbəʊt
In the Second World War (1939–45): a German minesweeper. Now historical.
Origin
1940s; earliest use found in The Times. From R + boat, after German R-Boot, shortened (after U-Boot) from Räumboot minesweeper from räumen to clear, clear away + Boot.