roil
Concise Oxford English Dictionary © 2008 Oxford University Press:
roil /rɔɪl/
▶verb
- 1 make (a liquid) turbid by disturbing the sediment.
■ (of a liquid) move in a turbulent manner.
- 2 US term for rile (sense 1).
– derivatives
roily adjective (N. Amer.).
roily adjective (N. Amer.).
– origin C16: perh. from OFr. ruiler ‘mix mortar’.
'roil' also found in these Oxford entries:

