noun
autographed baseball; signed ball
Refers specifically to a baseball that has been signed, typically by a player. A wasei-eigo term; in English one would say 'signed baseball' or 'autographed baseball'.
wasei-eigo (Japanese-coined English), from sign ball
彼は大谷選手のサインボールを宝物にしている。
He treasures an autographed baseball from Ohtani.
サインボールをもらうために、
I waited at the stadium after the game to get a signed ball.