Definition of "primer"
primer1
/ˈpɹaɪ.mə(ɹ)/
noun
plural primers
(historical, Catholicism ecclesiastical) A prayer or devotional book intended for laity, initially an abridgment of the breviary and manual including the hours of the Virgin Mary, 15 gradual and 7 penitential psalms, the litany, the placebo and dirige forming the office of the dead, and the commendations.
(New Zealand, obsolete) An elementary school class; an elementary school student.
primer2
/ˈpɹaɪ.mə(ɹ)/
noun
countable and uncountable, plural primers
(obsolete) A person who primes explosives.