1. Someone you know personally but is not officially your friend.
2. Someone you know during high school but will prolly never talk to him/her again after high school.

A person known vaguely, like someone you worked on a science project with once, and never really spoke to again. Maybe you have some mutual friends, but you wouldn't really go out and hang out with that person on your own. Someone who you say hi to in the halls at school, or maybe say hello when you see each other in public. In the simplest definition, someone you know well enough to say hi to, but aren't exactly friends with.

1) Someone who is one click above a total stranger, someone that you just know their name, but nor very well or that close.

2) Typically people that you see at work or at school that you never bother to see outside of those circumstances.

3) Typically your friend's friends that you run in to at a party or going out.

4) Not such a bad thing because at least they're not going to bother you or pressure you asking for favors or money to borrow.

When you masturbate with your non dominant hand for the second time in one day.

something you’ll never get

Somebody you say hi to on a daily basis but don’t associate with in depth. Or somebody you might slightly dispise but you still keep on good terms with.

"acquaintance" is such a complicated word. the dictionary says "a person one knows slightly, but not as a close friend"
that definition does not even begin to explain what an acquaintance is.
and acquaintance can be the example given by the dictionary. it can also be a person that you will not accept friendship from. it can be someone that you know almost everything about, yet you deny friendship of the said person. it can be a friend who you don't see that much, or don't feel close to. to be an "acquaintance" means much more than to not be friends. acquaintance can not really be defined in a few words, its just that type of thing that takes a laid out explanation rather than a definition. an acquaintance can range from anywhere between love and hate, and that doesn't mean it can't be either of the two. it could even be both at the same time.
an acquaintance can be many things
and i could go on and on about it, but i feel like i should stop here

and let you ponder

a person whose only interaction with you is when they post "Happy Birthday!" on your Facebook timeline

Someone who you are not dating but your not friends someone who may of slept with or kissed