Mad (Flt) Scientist:
Yes, I seem to recall that "vertical gusts" or similar terminology is used in both part 25 and part 23 certification requirements. Unless I'm missing the mark, this is primarily concerning the establishment of airspeeds at which up and down drafts of a an arbitrarily established velocity (50 fps up and 30 fps down seems familiar?) will not cause an exceedence of structural load limitations. I also recall seeing some reference to gust factor application somewhere in the certification flight test guide, perhaps in reference to takeoff and landing performance flight tests?
Since these particular uses of the term "gust" are not normally encountered in day to day line flying, I omitted them from my earlier post. However I'll concede that knowing how certain flight limitations and recommended speeds published in the AFM were established is useful. If for no other reason, a pilot aware of certification requirements and testing methodology seems more likely to have a proper respect for limitations and recommendations included in the AFM.