prefix
Productive prefix used in loanwords and modern compounds to mean 'partially' or 'half'. Common in words like セミプロ (semi-professional) or セミダブル (semi-double bed).
彼はまだセミプロの選手だが、実力はプロに近い。
He is still a semi-professional player, but his ability is close to that of a pro.
このホテルの部屋にはセミダブルのベッドがある。
This hotel room has a semi-double bed.