expression, godan verb (-u)
perform memorial rites for the deceased
Fixed expression used for conducting Buddhist or other religious ceremonies to pray for the repose of a soul after death.
家族で集まって、祖母の後を弔った。
The family gathered and performed memorial rites for our grandmother.
弔う is a general verb for mourning or holding a memorial service; 後を弔う specifically refers to rites for the repose of the deceased's soul after death.
The expression combines 後 (あと, 'after' or 'aftermath') with 弔う (とむらう, 'to mourn' or 'to hold a memorial service'), literally meaning 'to mourn the aftermath' or 'to perform rites after death'.