Know by Facebook 

When you recognize the name of someone in a conversation, but then realize that you only know them through facebook and have never actually met.

Disclaimer: Admitting this could cause you to sound like a creeper.

Person 1: Sorry we couldn't hang out, I was studying with (Insert Name) last night. Do you know him?
Person 2: Hmm, not by face, but I might know by Facebook.
Person 1: So that's a no?
Person 2: Pretty much.

Know by Facebook by Rockinroller September 3, 2010

...And You Will Know Us by the Trail of Dead

a rock band from Texas
often simply called "Trail of Dead"
a very good band and in my opinion the hope of alternative rock, a genre that suffered so much in the past few years.
they got everything: musical talent and the jolly good ambitions to bring variety into every album, cool lyrics, stylish artworks and on stage they simply ROCK! make sure to be there if they are around for a show.

i simply like ...And You Will Know Us by the Trail of Dead - although first i thought they play some emo crap. but then i listened to them!

...And You Will Know Us by the Trail of Dead by sgrDD March 20, 2008

i know you by heart

I know you ! (VERY WELL)

- I know you love Hannah !!!
- No I don't ..
- Oh stop I know you by heart ! You can't lie to me 😂

i know you by heart by Pascal cœur October 21, 2017

to know anything off by heart 

To learn something and keep it in mind for a longer time.

Synonyms:
To memorize
To learn by heart

Andy knows that it isn't easy for him to know anything off by heart.

to know anything off by heart by SmokingSkull January 22, 2011

hey, you know that song by that faggot?

Something homophobes say as a pick-up line to other homophobes as code to hook-up

I was at this truck stop standing near the pay showers when I heard this one trucker say to another, "hey, you know that song by that faggot?" I just grabbed my Code Red and Corn Nuts and went back to my car before I heard the answer.

hey, you know that song by that faggot? by von groovy February 21, 2019