something whose exact nature you do not know or have forgotten.

He's a professor of something or other and now he's living in China.

Related vocabulary: somehow or other

• That's just not cricket!
• that's life
• That's more like it.
• That's my story and I'm sticking to it.
• that's news to
• That's news to me.
• that's news to you
• That's not cricket!
• That's one for the books.
• That's rich!
• That's someone all over!
• that's that
• that's the nature of the beast
• That's the story of my life.
• That's the way the cookie crumbles.
• That was a ... and a half!
• That was a game and a half!
• That was a [game/meal/walk etc.] and a half!
• That was a meal and a half!
• That was a walk and a half!
• the ABCs of
• the ABCs of something
• the alma mater
• the answer to prayers
• the answer to someone's prayers