The bulk update request #13981 has been rejected.
Currently seems like a pointless and redundant tag with power armor. The wiki states that it's essentially for power armor that doesn't cover the whole body, which would seem to make it for things like post #5577936 or post #4390792, but instead the vast majority of the tag is just mistagged power armor or even mecha. In fact, out of 1535 posts in power suit, 735 are also tagged with power armor, most of which are either Samus Aran or Halo related.
Outside of those posts it's also being misused for posts of power armored character with their helmets off (post #4878065, post #4652413, post #4505854), and completely unrelated images like post #5747339 (superhero leotard), post #4999623 (pilot suit), and post #4295784 (mecha musume).
Danbooru's current definition of power suit as "power armor that doesn't cover the whole body" doesn't seem to exist anywhere else either. Googling power suit mostly gives fashion-related results and the Metroid wiki, while wikipedia simply includes it in a long list of synonyms for powered exoskeleton, which is the term they use to refer to both what we tag as exoskeleton and power armor.