underheats

/ˌʌndərˈhiːts/
verb
  1. Third person singular form of underheat; heats something less than needed.
    • The oven often underheats the bottom of the pizza, leaving it doughy.
    • The machine underheats the plastic, making it difficult to mold.
    • He underheats the water for his tea, so it never gets hot enough.