impale (someone, something, or oneself) on (something)
1. To stab someone or something with something. They used to impale their victims on pikes, I swear!
2. To be stabbed with or by something. In this usage, a noun or pronoun is used between "impale" and "on." You're going to impale yourself on one of those sharp rocks if you're not careful!
impale someone or something on something
to put someone or something on a pointed object and press down. The crowd had impaled an effigy of the dictator on a sharpened stick. The waves almost impaled me on a submerged tree branch.