calm air

English Thesaurus

1. wind moving at less than 1 knot; 0 on the Beaufort scale (noun.phenomenon)

hypernym	:	air current, current of air, wind,
definition	:	air moving (sometimes with considerable force) from an area of high pressure to an area of low pressure (noun.phenomenon)

part meronym	:	beaufort scale, wind scale,
definition	:	an international scale of wind force from 0 (calm air) to 12 (hurricane) (noun.linkdef)