What do you mean by “na mehram” in Islam?

the one is outside of your family and not allowed to see you without hijab/veil and Mahrams who are opposite of the word are different because father and son and brother are mahrams but a girl can’t be naked and intimate with them but with husband she can do such things

mahram: the women/men that you are not allowed to marry, they are generally though not strictly very close relative and have blood relationship like -

for men :mother, daughter,sister(female sibling), sisters of your mother, grand mothers etc.

for women: father,son,brother(male sibling),uncle(maternal as well), grandfathers etc.

na mahram: the women/men that you are allowed to marry. It includes all women/men other than mahram( including cousins).

The important thing is looking at mahram for men are allowed(in general case apart from parts from below the neck to toe, for exact rulings go to the link given below ) but looking at namahram with or without sexual desire is prohibited.

A women can see both mahram and namahram( apart from the parts from below the belly button to the knees). But looking at a man encites her sexual desires, she can't see the man,it is prohibited.

exception: wife/husband is also mahram bit ruling are different for them.

exception: there are some mahram such that though you can not marry them but you can not look at them either.

there are also many exceptions and different rulings

for details:

details of mahram/namahram

https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://islamqa.info/en/5538&ved=2ahUKEwj6z5nJpOrdAhXFtY8KHY4xDi4QFjAAegQIARAB&usg=AOvVaw2R5vqfyuOadj_GFwzT-g42

details of rulings for looking at mahram/namahram

https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://www.al-islam.org/code-ethics-muslim-men-and-women-sayyid-masud-masumi/rules-related-looking-others&ved=2ahUKEwj6z5nJpOrdAhXFtY8KHY4xDi4QFjAJegQIAxAB&usg=AOvVaw2mln_hPuh_MPCvymEPuSrf

body parts forbidden for mahram to look at

https://www.google.co.in/url?sa=t&source=web&rct=j&url=http://www.daruliftaa.com/node/5413&ved=2ahUKEwj6z5nJpOrdAhXFtY8KHY4xDi4QFjAKegQICBAB&usg=AOvVaw3pfBp2qMRqB6pu42uPi25X

the women/men that you are not allowed to marry, they are generally though not strictly very close relative and have blood relationship like -

for men :mother, daughter,sister(female sibling), sisters of your mother, grand mothers etc.

for women: father,son,brother(male sibling),uncle(maternal as well), grandfathers etc.

Icezy fun

Na mehram are those men …..from.them.the Muslims girls should cover their faces and bodies . Except grandfather,father ,brother,husband,maternal.amd paternal uncles ..all other males are na mehram for a girl.

The word Na Mahram came from urdu word "Mahram" means "known". Similarly the word na Mahram means unknown for somebody or having no relation with that person . We may say that the na Mahram person is just like the any person of world having no relation other than that of humanity

With whom are can marry, are Na mahram.
and you are not allowed to be with them without parda

All those whom you are allowed to marry are your Na Mehram.
All those whom you are not allowed to marry Plus the one you are already married are your Mahrem.

Anyone you can have sex with is na mahram.

Whereas mahram is some you can't have sex with that is any random man outside your family .

Someone who you may not shake hands with, and someone who should not see your hair if you are a female and have reached the stage of baligha (adolescents)

A mahram is any male who you are allowed to be infront of without hijab in basically. So your direct uncle, your father, your brother, your female relatives(i.e female cousins), your grandparents and your husband. For the male, the mahram would be their sister, their father, their mother, their direct aunt, male relatives (i.e. male cousin)s and their grandparents. A non mahram would basically be the opposite of that.