Quote Originally Posted by paulb
"leisurely" doesn't work well in that sort of sentence. For some reason there are only a few expressions where we use "leisurely" in English, and exhale is not one of them. (lazily is fine)
I disagree. To me, "leisurely" sounds ok here, but it depends on the verb used in the translation. No word is an island.

"Easily" sounds bad altogether.

"Leisurely" may not be best with the word "exhale", but as a translation for the word "неторопливо" in this context, it's good.

"and leisurely lets a stream of smoke drift from his mouth." or, maybe better:
"and lets a stream of smoke drift lazily from his lips." (We would probably not say "mouth" here because it sounds like a wide-open mouth.)

To me, "lazily" works only if it modifies that action of the smoke, not the person. It sounds dumb to say that a person blows smoke lazily -- as if anybody does it any other way.

To sum up:

How did the man act? Leisurely, or unhurriedly.
How did the smoke move? Lazily.

Which you use just depends on how you structure your sentence.