WordNet sense 1 (a cry of sorrow and grief):

lamentation, plaint, wail

WordNet sense 2 (a song or hymn of mourning composed or performed as a memorial to a dead person):

coronach, dirge, requiem, threnody

WordNet sense 3 (a mournful poem; a lament for the dead):

elegy

WordNet sense 4 (express grief verbally):

keen

WordNet sense 5 (regret strongly):

bemoan, bewail, deplore