undercolour

• undercolor

From under- +‎ colour.

• Audio (US):

  (file)

undercolour (plural undercolours)

1. A colour used as a base and then coloured over, as in watercolour painting.
2. The colour of the underparts of a bird, rabbit, etc.

undercolour (third-person singular simple present undercolours, present participle undercolouring, simple past and past participle undercoloured)

1. (transitive) To colour insufficiently.