off the top of your head
US /ɔf ðə tɑp əv jʊər hɛd/
UK /ɔf ðə tɑp əv jʊər hɛd/
1.
from memory, without careful thought or checking facts
:
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I can't tell you the exact number off the top of my head, but it's around fifty.
•
Can you name three capital cities off the top of your head?