frost

frost 1

•  noun
• 

1    [U] a white powder of ice, which forms on surfaces outside when the temperature is very cold:
?trees covered with frost
2    [C] very cold weather, when water freezes:
?an early frost
?a hard frost (= extremely cold weather)

frost 2

• verb [T] AmE

to cover a cake with FROSTING ; ICE BrE