tailwind

From tail +‎ wind.

• IPA^(key): /ˈteɪlwɪnd/

tailwind (plural tailwinds)

1. (nautical, physics) A wind that blows in the same direction as the course taken by an aircraft, sailing ship, bird, etc.
2. (figurative, by extension) A force that accelerates progress.

• headwind

tailwind (third-person singular simple present tailwinds, present participle tailwinding, simple past and past participle tailwinded)

1. Of a wind, to blow on a windmill or wind turbine in such a way that wind pressure is exerted on the wrong side of the sail or turbine assembly.