sub-zero

UK: /ˌsʌbˈzɪərəʊ/ US: (sub zēr′ō)

WordReference Random House Unabridged Dictionary of American English © 2026

sub-ze•ro  (sub zēr′ō), adj. 

1. indicating or recording lower than zero on some scale, esp. on the Fahrenheit scale:
   a week of sub-zero temperatures.
2. characterized by or appropriate for sub-zero temperatures:
   sub-zero climates; sub-zero clothing for the exploration.

• sub- + zero