What does foid mean?
"Foid" is a clipped form of "feldspathoid," a term petrologists use for a family of minerals—such as nepheline, leucite, and sodalite—that resemble feldspar in structure but are deficient in silica. Because these minerals can only crystallize in magmas low in silica, their presence is diagnostic: rocks rich in them, like foid syenites and foidites, signal silica-undersaturated conditions deep within the Earth. The abbreviation appears in classification schemes such as the QAPF diagram, making "foid" convenient shorthand in technical descriptions of alkaline rocks. Separately, "foid" has been adopted as a derogatory slang term for women within certain misogynistic online communities, derived from the earlier portmanteau "femoid." This slang usage is deeply offensive and dehumanizing, and reputable writing avoids it entirely. Readers encountering "foid" should therefore rely on context: in scientific literature it names a legitimate mineral group, while elsewhere it signals hostile intent.
A feldspathoid mineral—a tectosilicate such as nepheline, leucite, or sodalite—found in silica-undersaturated igneous rocks.
"This foid syenite owes its low density to abundant nepheline."
'Foid' is accepted technical shorthand in petrology, especially in IUGS rock classification.
(Derogatory internet slang) A woman, used pejoratively in misogynistic online communities; a clipping of 'femoid'.
"Use of the slur in that forum drew widespread condemnation."
Highly offensive; avoid entirely.
Regular plural; used both for mineral occurrences and, offensively, in slang contexts.
"Thin-section analysis revealed foids intergrown with alkali feldspar."
"Foid" lives a double life: a respectable geology shorthand on one side, and one of the internet's most notorious slurs on the other — context is everything.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of foid
The geological term "foid" arose as an abbreviation of "feldspathoid," itself formed from "feldspar" plus the Greek-derived suffix "-oid" (from "-oeidēs," meaning 'form' or 'resemblance'), denoting minerals resembling feldspar. The slang usage developed from "femoid," a blend of "female" and the same "-oid" suffix popularized in pseudoscientific online discourse, and its clipping to "foid" spread through those communities; it has no connection to the geological term beyond the shared suffix.
Related word forms
How foid is actually used
The geological sense is neutral, technical shorthand used mainly in petrology and mineral classification schemes such as the QAPF diagram, where 'foid' stands in for 'feldspathoid'. The slang sense is highly offensive, associated with misogynistic online spaces, and should not be used; it derives from the portmanteau 'femoid' and carries strong dehumanizing connotations.
Easily confused with foid
Feldspars are silica-rich framework silicates, whereas foids (feldspathoids) are silica-poor minerals with a similar structure that form only in silica-undersaturated rocks.
Not applicable — this confusion does not exist.