When a girl's hair is so long that when she is naked, her hair will cover her boobs entirely. Much like in some images of mermaids.
Betty: I have such mermaid hair right now!
Lisa: Dammit, mine's only shoulder-length.
by sc00b July 19, 2009
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Hair that is long, flowing, and has a beach-y look to it that makes the person look like a mermaid, hence the name.
Wow, you have such beautiful mermaid hair. It makes you look glorious and fierce.
by melinda jeanene May 5, 2008
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Hair that is long, flowing, silky, healthy, and shiny. There are no split ends or fly-a-ways and it is incredibly soft. It is usually wavy. Mermaid hair looks good wet, too. Mermaid hair may be a component of extensions or natural hair, but wigs do not count. Natural mermaid hair is far more impressive than fake, wanna-be mermaid hair.

It takes patience and discipline to get mermaid hair, as most people are not born with it. One cannot use hair dyes, perms, other chemicals, or heat. Mermaid hair cannot be damaged. Vitamins and minerals may be taken to nourish new growth and coconut or argan oils may be used as humectants to help moisturize hair. Eat lots of protein, drink lots of water, and take a multivitamin. You may even want to consider keeping a shoe box filled with vitamins and minerals.

Trim dead/split ends so you don't end up with splitting, unhealthy hair strands. It's better to have healthy hair/ends than length any day, even for mermaid hair.

If you have hormonal imbalances or any form of alopecia (hormonal or hereditary,) it will be harder for you to obtain mermaid hair. Over-the-counter products like Rogaine can help women who've lost hair due to hormonal issues, but do not expect to get mermaid hair right away. Also, vitamin D and iron deficiencies can cause hair loss, so you may want to get blood tests done if you think supplements may help you get mermaid hair.

Do not use hair brushes. Instead, use wide-toothed combs or fro combs.
That girl sitting over there has mermaid hair!!!

mermaid hair health beauty care
by Mermaidologist June 18, 2013
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A girls hair when she first wakes up and has no product in it. It is usually wavy and untamed. Girls usually proceed to add masses of chemicals and straighten the shit out of it.
Girl: I just woke up and my hair looks like shit!
Girl 2: No it's beautiful! It's princess-mermaid hair!
by kupkake2015 November 28, 2012
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