The buttocks.
The anus.
The natural features of a land surface unaltered by humans.
A foundation, as of a building.
An underlying theoretical basis or principle: "All neighbor states ... must revise ... their policy fundaments" (C.L. Sulzberger).
"Alle þe filþ of his magh ['maw'] salle breste out atte his fondament for drede." ["Cursor Mundi," c.1340]
fundament fun·da·ment (fŭn'də-mənt) n. See anus.