Apris
Apri (āprī) in Sanskrit means "conciliation, propitiation" and refers to special invocations spoken previous to the offering of oblations in an animal sacrifice. Some scholars have proposed however, that these hymns were originally meant for a family ritual centered around Agni, which was then later connected to the animal sacrifice.

Aprisuktas
Of the ten Aprisuktas mentioned in Gargya Narayanas commentary,  I.13 and I.142 both invoke  the Narāśaṁsa and Tanūnapāt manifestations of Agni, I.188, III.4, IX.5 and X.110 invoke only the Tanūnapāt manifestation and II.3, V.5, VII.2 and X.70 invoke only the Narāśaṁsa manifestation.

References

āprī in: Monier-Williams A Sanskrit Dictionary, 1899.
R. Fick, "Gotra" in: ed.  Hastings, Encyclopaedia of Religion and Ethics vol. 6, 1999, p. 355
Samir Nath, "Gotra-system" in: Dictionary Of Vedanta, 2002, p. 153.