The act or process of flattening or making flat; the state of being flattened.
From Latin complanatio, derived from complanare (to flatten). The -tion suffix converts the verb to an abstract noun. This technical term developed in botanical and medical contexts during the 17th-18th centuries.
This word is so specialized that even many botanists would need to look it up—it's a perfect example of how technical fields develop their own precise vocabulary that the general public never encounters.
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