The correct spelling of the phrase "does top of head" is "off the top of my head." The pronunciation of this phrase is /ɒf ðə tɒp əv maɪ hɛd/. In this phrase, the word "off" is spelled with two Fs and is pronounced with the short vowel sound /ɒ/. The word "the" is spelled with a silent E at the end and pronounced with the schwa sound /ðə/. The word "of" is pronounced with the schwa sound /əv/. Finally, "my" is pronounced with the long vowel sound /maɪ/ and "head" is pronounced with the short vowel sound /hɛd/.
There is no lexical phrase or specific term called "does top of head" in dictionaries. However, it seems like you might be referring to the phrase "off the top of one's head" or "off the top of my head." In that case, here is the definition:
"Off the top of one’s head" is an idiomatic expression that means providing an immediate answer or response without much thought or prior preparation. It refers to giving a spontaneous reply based on one's initial instinct or general knowledge, rather than relying on in-depth analysis or research. When someone answers a question "off the top of their head," they are offering an initial impression or estimate, which may not be completely accurate or well-reasoned due to the lack of time for reflection.
For example, if someone asks for the population of a specific city and you respond by saying "around one million, off the top of my head," it means you are providing an approximate figure based on your general knowledge, without consulting any sources or conducting a thorough investigation. The phrase is often used to acknowledge that the answer may not be entirely precise but is given as a starting point or a rough estimation.