From harvest +‎ -er.

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harvester (plural harvesters)

1. (dated) A person who gathers the harvest (harvests the crop).

   Hypernym: person

   Hyponym: harvestman

2. A machine that gathers the harvest (harvests the crop).

   Hyponyms: combine harvester, combine

   Coordinate term: harvestman

3. (forestry) A type of heavy forestry vehicle employed in cut-to-length logging for felling, delimbing and bucking trees; an instance of this type.
4. (computing) A program or algorithm that gathers data from a source.
5. A North American butterfly species, Feniseca tarquinius, whose larvae eat aphids and are the only entirely carnivorous caterpillars in North America; an individual of this species.
6. Any butterfly of the lycaenid subfamily Miletinae to which this belongs, which are all carnivores.
7. (Ireland) A finnock (a young sea trout).

(person or machine):

• Everharts, reharvest