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]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

INFRA, Latin. Below, under, beneath, underneath. The opposite of supra,
above. Thus we say primo gradu est supra, pater, mater; infra, filius,
filia. In the first degree of kindred in the ascending line; above, is the
father and the mother; below, in the descending line, the son and daughter.
Inst. 3, 6, l.
     2. In another, sense, this word signifies within; as, infra corpus
comitatus, within the body of the county; infra proesidia, within the
guards.
     3. It also signifies during; as infra furorem during the madness.