Offhand means without preparation or deep thought, in a casual or spontaneous way. When you answer a question offhand, you respond immediately based on what you know at that moment, without checking facts or carefully considering your words. A teacher might say offhand that there are about 200 countries in the world, meaning she's giving a quick estimate without looking it up.

The word can describe both how someone does something and the casual attitude behind it. If your friend asks what time soccer practice starts and you say “three o'clock” offhand, you're answering quickly from memory. But if someone dismisses your idea in an offhand way, they're treating it too casually, perhaps without giving it the serious consideration it deserves.

You might say “I can't tell you offhand” when someone asks something you'd need to look up or think about more carefully. The phrase suggests honesty: you're admitting you don't have the answer ready at that moment. While offhand responses work fine for casual questions, important decisions deserve more than offhand answers.