Within a spiritual context, a litany is a long, repetitious series of prayers, invocations, and supplications often led by a priest/ess with responses from the group. These are often rhythmic and chant-like.
In common speech, the word litany often refers to a list or a series on a theme. As in “a litany of complaints”.
A common use of the word litany in Pagan spirituality is the Litany of the Dead. This is a list of names of those who have died read by a ceremonial leader with or without a response from the group. It is a common Samhain practice to read a Litany of those who died the year before or the beloved dead of those present, or a combination of both.