Wiktionary
calm wind
n. (context US aviation English) wind that is slower than 3 knots.
Usage examples of "calm wind".
Thunderheads were massed to the west, approaching at a slow, steady roll across the back of a still-calm wind, and the burn of the sun through gaps in the thinner clouds east was giving way before cooler air.
The sails flapped loosely in the near calm wind, and the sea heaved smooth and glassy as if heavy grease floated upon its surface.