A disappointed/dejected kaomoji, "shoboon" (´・ω・`) [ｼｮﾎﾞｰﾝ]. Also known as the "denko" kaomoji after a story which used this face frequently. Originates from 2channel.
For Danbooru's purposes, this tag also refers to the short-vowel version, "shobon" (́・ω・) [しょぼん].
