What is Fill?

Legal Definition
To make full; to complete; to satisfy or fulfill; to possess and perform the duties of. The election of a person to an office constitutes the essence of his appointment; but the office cannot be considered as actually filled until his acceptance, either express or implied. Johnston v. Wilson, 2 N. H. 202, 9 Am. Dec. 50. Where one subscribes for shares in a corporation, agreeing to "take and fill" a certain number of shares, assumpsit will lie against him to recover an assessment on his shares; the word "fill," in this connection, amounting to a promise to pay assessments. Bangor Bridge Co. v. McMahon, 10 Me. 478. To fill a prescription is to furnish, prepare, and combine the requisite materials in due proportion as prescribed. Kay v. Burbank, 61 Ga. 505, 34 Am. Rep. 103.
-- Black's Law Dictionary