The crossword solution for the term 'Lamentation (Poet.)' is 'PLAINT, ' which is a six-letter word. A PLAINT is a type of poem or song that expresses sorrow or grief. It is often used in literature to express the feelings of a character or narrator. Lamentations, specifically, are a type of PLAINT that are traditionally used to mourn the dead. They are often found in religious texts and are used to express grief over a loss.