From hierateuo; the priestly fraternity, i.e. Sacerdotal order (figuratively) -- priesthood.
see GREEK hierateuo
a. the office of priest.
b. the order or body of priests (see ἀδελφότης, αἰχμαλωσία, διασπορά, θεραπεία); so Christians are called, because they have access to God and offer not external but 'spiritual' (πνευματικά) sacrifices: 1 Peter 2:5; also βασίλειον ἱεράτευμα, 1 Peter 2:9 (after Exodus 19:6, the Sept.), priests of kingly rank, i. e. exalted to a moral rank and freedom which exempts them from the control of everyone but God and Christ. (Exodus 23:22, etc.; 2 Macc. 2:17); not found in secular authors.)