Lit. "Nature." Certain ancient practices of the prophets before the time of Muhammad which have not been forbidden by him.‘Ayishah relates that the Prophet said: "There are ten qualities of the prophets - clipping the mustachios so that they do not enter the mouth, not cutting or shaving the beard. Cleansing the teeth (i.e. miswak), cleansing the nostrils with water at the usual ablutions, cutting the nails, cleaning the finger joints, pulling out the hairs under the arm pits, shaving the hair of the privates, washing with water after passing urine, and cleansing the mouth with water at the time of ablution." (See Sahih Muslim.) ... (Hughes' Dictionary of Islam)
The primordial norm; a harmony between man, creation, and God, such as existed between God and Adam in the Garden. ... The concept of fitrah, the primordial norm, is at once the measure of truth in our actions and being, and at the same time the quality of harmony between ourselves and the cosmos. (Glassé, Concise Encyclopedia of Islam)
Another, rarely used meaning of fitrah is that
of a charity that is due on Eid al-Fitr,
on the night after Ramadan.