You are given a link to something (say a video) but when you follow the link, you get something like a Rick Astley music video on Youtube - you've been rickrolled!

rickroll, The internet theme song.

Tricking someone into clicking a link that leads to the music video of the song "Never Gonna Give You Up" by Rick Astley, not Reddit's stupid put a picture of Rick Astley in this corner of the meme or have a part of the video at the end of the video or having the words "never gonna give you up" hidden in the meme with some text guiding you towards where it is

Full Rick roll definition:

A Rick roll is a very good way to tick someone into watching this

We're no strangers to love
You know the rules and so do I
A full commitment's what I'm thinking of
You wouldn't get this from any other guy

I just wanna tell you how I'm feeling
Gotta make you understand

We've known each other for so long
Your heart's been aching, but
You're too shy to say it
Inside, we both know what's been going on
We know the game and we're gonna play it

And if you ask me how I'm feeling
Don't tell me you're too blind to see

Never gonna give you up
Never gonna let you down
Never gonna run around and desert you
Never gonna make you cry
Never gonna say goodbye
Never gonna tell a lie and hurt you

Never gonna give you up
Never gonna let you down
Never gonna run around and desert you
Never gonna make you cry
Never gonna say goodbye
Never gonna tell a lie and hurt you

(Ooh, give you up)
(Ooh, give you up)
Never gonna give, never gonna give
(Give you up)
Never gonna give, never gonna give
(Give you up)

We've known each other for so long
Your heart's been aching, but
You're too shy to say it
Inside, we both know what's been going on
We know the game and we're gonna play it

I just wanna tell you how I'm feeling
Gotta make you understand

Never gonna give you up
Never gonna let you down
Never gonna run around and desert you
Never gonna make you cry
Never gonna say goodbye
Never gonna tell a lie and hurt you

We're no strangers to love
You know the rules, and so do I!
A full commitment's what I'm thinking of
You wouldn't get this from any other guy
I just wanna tell you how I'm feeling
Gotta make you understand
Never gonna give you up
Never gonna let you down

Never gonna run around and desert you
Never gonna make you cry
Never gonna say goodbye
Never gonna tell a lie and hurt you
We've known each other for so long
Your heart's been aching but you're too shy to say it
Inside we both know what's been going on
We know the game and we're gonna play it
And if you ask me how I'm feeling
Don't tell me you're too blind to see
Never gonna give you up
Never gonna let you down

Never gonna run around and desert you
Never gonna make you cry
Never gonna say goodbye
Never gonna tell a lie and hurt you

An internet meme.
When an user is tricked into watching Rick Astley's song "Never gonna give you up", it's called to rickroll (v) and a person who ends up in the rickrolling has been rickrolled
Even celebrities have been victims of rickrolling as seen in this video: youtu.be/oHg5SJYRHA0