Hey Kate! If you say something off the top of your head, you say it without thinking about it much before you speak, especially because you do not have enough time. Here you have some examples: There are some good restaurants around here, but I can't tell you their names off the top of my head. "Do you remember her name?" "Not off the top of my head."• I keep doing stuff off the top of my head. "How much is the house worth?" "Off the top of my head, I'd say it's worth maybe $160,000."