vârun, vâgard (#)
Fr.: contraire, opposé
Opposite or contrary in position, direction, order, etc.
M.E. revers from O.Fr. revers "reverse, cross," from L. reversus, p.p. of revertere "to turn back," from → re- "back" + vertere "to turn," cognate with Pers. gard "to turn," as below.
Vârun "inverse, upside down," from vâ- "back, backward, again, re-,"
variant of bâz-, from Mid.Pers. abâz-, apâc-, O.Pers. apa- [pref.]
"away, from;" Av. apa- [pref.] "away, from,"
apaš [adv.] "toward the back;" cf. Skt. ápāñc
Fr.: choc en retour
A → shock front in a → supernova remnant (SNR) arising from the interaction of the → supersonic → forward shock wave with the → interstellar medium (ISM) material. The reverse shock forms as the high pressure gas behind the forward shock wave expands and pushes back on the stellar ejecta. Reverse shock propagates into ejecta, starting from outside.