Lewis & Short

conceptīvus, a, um, adj. [concipio].

  1. * I. That is conceived: fides et dilectio non substantiva animae sed conceptiva, Tert. Res Carn. 40.
  2. II. That is ordered, directed; so only feriae, in the Roman ritual, those festivals that were not fixed for a certain day, but were celebrated annually on days appointed by the priests or magistrates, movable festivals. Such were the Compitalia, Paganalia, Sementivae, Latinae, etc., Varr. L. L. 6, § 26; Macr. S. 1, 16; cf. Paul. ex Fest. p. 62, 15 Müll.