noun, noun which may take the genitive case particle 'no', na-adjective
tallness; tall person
Refers to the quality of being tall or to a tall person. Often used as a noun or adjectivally with の or な.
彼は背高の男性だ。
He is a tall man.
背高な植物が庭に生えている。
Tall plants are growing in the garden.
背が高い is the more common phrase meaning 'tall' (literally 'back is high'). 背高 is a less common noun/adjective form.
Compound of 背 (se, 'back, stature') and 高 (taka, 'height'). The exact historical derivation is uncertain, but it is a straightforward combination meaning 'tall stature'.