Since a good number of people come to this site in a google search for the meaning of "oremus pro invicem", I thought I would post it (again-I'm sure I have done it in the past.)
Oremus pro invicem translates Let us pray for each other.
I first saw it on the ordination card of a priest in the diocese of Boston who is very close to our family. Since then we have made it an addendum to our family morning prayer. Hopefully we take it to heart and do pray for each other throughout the day.