(colloquial) Clipping of 意味深長 (imishinchō).

meaningless

meaningful; suggestive; significant

zero on a test etc., no points earned / freezing point / zero (value of a function’s independent variables when the value of the function is zero)

to turn on, to switch on

(education) The 1,026 kanji taught in primary school; a subset of 常用漢字 (じょうようかんじ, jōyō kanji)

smaller kanji historically used as a pronunciation guide, similar to modern furigana

kanji approved for regular use by the 文部科学省 (Monbu-kagaku-shō, “Japanese Ministry of Education”)

Sino-Korean vocabulary or "Hanja-eo"

The iteration mark 々, which indicates that the previous kanji ought to be repeated.