Dictionary.net

• A tendency to turn or bend in opposition to gravity or away from the centre of the earth, as opposed to GEOTROPISM (which see). Darwin.

1899 - The american dictionary of the english language.
By Daniel Lyons

• Tendency to act apparently contrary to law of gravity-this is, to turn away from the earth.

1920 - A dictionary of scientific terms.
By Henderson, I. F.; Henderson, W. D.