横

either side of a rikishi's mawashi

spotstripe snapper (species of fish, Lutjanus ophuysenii)

strike-slip fault

horizontal friction; strike-slip

Internet slang

butting in (to a discussion on a message board, mailing list, etc.); reply from someone who has butted in

Metagonimus yokogawai (species of intestinal fluke)

half-pass (horse gait)

Computing

double-width size (of text)

joining both chopsticks together and using them as a spoon (breach of chopstick etiquette)

cross-sectional data

humpnose big-eye bream (Monotaxis grandoculis); bigeye emperor

Slang

side boob (side of a woman's breast exposed by clothing)

Yokoyama Shinto (Edo-period Shinto sect promoted by Masae Yokoyama)

transverse temporal gyri; ridges on the cerebral cortex; Heschl's gyri; Heschl's convolutions

transverse section

cross-cut; crossline; transversal; transverse line

crossing boundaries (structural, organizational, etc.)

Oft. adverbially as 〜に

(running) abreast; side-by-side; in a row

neck and neck; (almost) equal

line abreast; rank

landscape-oriented; transversely oriented

person crossing (e.g. the road); traverser

horizontal deployment (of techniques, etc.); application to other fields

rigging; shrouds

underpass; underground crossing