to think very hard about something
何かについて一生懸命考える (nanika ni tsuite isshoukenmei kangaeru)
"I had to rack my brains to remember her name."
"彼女の名前を思い出すためにrack my brainsしなければならなかった。" (Kanojo no namae wo omoidasu tame ni **rack my brains** shinakereba naranakatta.)
