Hekomi is a Japanese go term, literally meaning "sink" or "(in)dent", referring to the type of easy-to-overlook move shown here, which is the only way Black can live.
maruseru: The japanese term in the CJK box is given in katakana, but JEDict also has a kanji for the term: "凹み (HEKOMI) hollow, cavity, dent, depression." I think the kanji 凹 is a really good depiction of a dent.
hnishy: Some kanjis are in fact pictograms. 凸 is protrusion.