背甲 is read as せごう (segou) and means back.
せごう
segou
せたけ
stature
せすじ
seam down the back (of clothing)
はいきんりょく
strength of one's back
はいはんこうい
act of disobedience (betrayal)
はいけいはんしゃりつ
background reflectance
はいしんこうい
breach of faith
はいけいほうしゃ
background radiation
はいけいまく
backdrop
はいすいのじん
fighting with one's back to the wall
はいとくかん
sense of guilty pleasure
せひょう
collating mark
はいりん
copying from a model without looking at it (calligraphy)