underwash

From under- +‎ wash.

• Audio (US):

  (file)

underwash (third-person singular simple present underwashes, present participle underwashing, simple past and past participle underwashed)

1. (transitive) To wash too little or too infrequently.
2. (transitive) To wash beneath.
   • 1847 March 30, Herman Melville, Omoo: A Narrative of Adventures in the South Seas; […], London: John Murray, […], →OCLC:

     Right on the beach was a mighty old cocoa-nut tree, the roots of which had been underwashed by the waves so that the trunk inclined far over its base.