The Collaborative International Dictionary of English v.0.48:

Infra \In*"fra\, adv. [L. Cf. Inferior.]
   Below; beneath; under; after; -- often used as a prefix.
   [1913 Webster]

WordNet (r) 3.0 (2006):

infra
    adv 1: (in writing) see below; "vide infra" [syn: below,
           infra]