the six-character name of Amida Buddha
Specifically refers to the nembutsu phrase 南無阿弥陀仏 (Namu Amida Butsu) when written as six Chinese characters. Used in Pure Land Buddhist practice.
See also: 六字の名号 · 南無阿弥陀仏 (なむあみだぶつ)
In the Jōdo sect, reciting the six-character name is considered important.
The six-character name is written on the hanging scroll.
The actual nembutsu phrase; 六字名号 refers to the written form of this phrase as six characters.
From 六字 (six characters) + 名号 (name/title), referring to the six-character written form of the nembutsu.