The word comes from the French oustre (also spelled ouster), which is an infinitive, and French infinitives can be used similarly to gerunds, so your intuition about it being equivalent to "ousting" is right, it's just that your English-speaker brain wants to analyze it as "one who ousts" instead of "to oust."Yarjka wrote:Ouster (n.)
3. Law The act of forcing one out of possession or occupancy of material property to which one is entitled; illegal or wrongful dispossession.
This word has been used a lot here in Toronto since the ouster of Mayor Rob Ford. I think it is very bizarre to see the -er ending describing an action rather than a person who does the action. 'Ousting' seems like the more natural term to me, but I guess I'm wrong.
(Apparently I'm going to comment on the etymology of a lot of the words posted here, so you all have that to look forward to.)