One who impales; someone or something that pierces or runs something through.
From empale + -er (agent suffix that creates nouns for one who does the action). The -er suffix is English's most productive way to create agent nouns.
The -er suffix is so powerful that it can turn almost any verb into 'one who does it'—an empaler is simply 'one who impales,' showing how English builds vocabulary economically by reusing productive suffixes.
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