SU means WITH
His as of his pants '' su pantalon''
Su autorización - Its okay
Su hyun
It can mean "your" (formal) or his, or her.
"Su casa" means "your house."
"Su hermana" means "his/her sister" in English.
"Su amigo Pedro" means "his/her friend, Pedro"
Estoy a su bebe in English means I am a baby.
"Su mano derecho" means "his/her/your right hand."
While some people refers it to InstaGram. The most common acronym for InStaGram is "Insta" or "ISG".
"Su hermano" in Spanish means "his brother" or "her brother," depending on the context in which it is used.