Anvil Cloud(redirected from anviltop)
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anvil cloud[′an·vəl ‚klau̇d]
a cumulonimbus cloud whose top part is flattened out in the shape of an anvil of solid or fibrous structure and has a bright white color in sunlight. The anvil cloud consists of ice crystals and forms when a cumulonimbus cloud reaches a level with a temperature on the order of —10°C and lower.