We found one dictionary that defines the word upper surfaces:

General (1 matching dictionary)

1. upper surfaces: Vocabulary.com

(Note: See upper_surface as well.)

Definitions from WordNet (upper surface) ▸ noun:  the side that is uppermost ▸ Also see upper_surface ▸ Words similar to upper surfaces ▸ Usage examples for upper surfaces ▸ Idioms related to upper surfaces ▸ Wikipedia articles (New!) ▸ Words that often appear near upper surfaces ▸ Rhymes of upper surfaces ▸ Invented words related to upper surfaces