Real Dictionary

lament
Someone's lament is an expression of their sadness, regret, or disappointment about something.
verb: If you lament something, you express your sadness, regret, or disappointment about it.

lament in American English
an outward expression of sorrow; lamentation; wail
to feel deep sorrow or express it as by weeping or wailing; mourn; grieve
to feel or express deep sorrow for; mourn or grieve for
intransitive verb: to feel, show, or express grief, sorrow, or regret
noun: an expression of grief or sorrow
transitive verb: to feel or express sorrow or regret for

lament in British English
noun: an expression of sorrow
verb: to feel or express sorrow, remorse, or regret (for or over)