noun
trial club membership; joining a club on a trial basis
Used in school or extracurricular contexts when someone participates in a club's activities for a short period before deciding whether to formally join.
新入生はまず体験入部をしてみるといいですよ。
New students should try out a club first through a trial membership.
彼はバスケ部に体
He joined the basketball club on a trial basis and then became a full member.