One who gashes; something that causes gashes or deep cuts.
From 'gash' plus the agent noun suffix '-er,' creating a noun for something or someone that performs the action of gashing.
Agent nouns with '-er' are one of English's most productive word-building patterns—you can add '-er' to almost any verb and create a new word, which is why 'gasher' is instantly understandable even if rarely used.
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