isabnormal

American  

[ahy-sab-nawr-muhl] / ˌaɪ sæbˈnɔr məl /

noun

Meteorology.

1. a line on a map or chart connecting points having an equal deviation from the normal value of some meteorological quantity, as temperature.

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Etymology

Origin of isabnormal

First recorded in 1850–55; is- + abnormal