A stranger/unknown person. Usually a friend of a friend.

the whale tail is the shape formed when a g-string rides up high over a womans trousers

Random people. People you don't know, and who seem to be there for no reason. Strangers, or barely-there acquaintances.
The ones nobody invited to the party, but who hang around anyway - no-one will ask them to leave, as no-one knows who invited them in the first place.

Someone you meet on a night out who noone knows but you remember later usually the next day

Someone of no real significance or importance in your life, who's just kind of there as part of the human population waiting to return to their nest. They could someday be important to you, but until then they are still just a randomer.

Synonym for 'random' - a person unknown to a group or one who says/does things which are inconsequential, makes contributions which are unconnected with the topic under discussion or behaves in ways which do not match the norms of a group or sub-culture.

A new clique, but a rare one that isn't found at every school. You may consider randomers immature but they can't help it, just like emo's can't help being pussies. Randomers do not use stupid words like 'cheese' and 'monkey'. An example of a Randomer's behaviour will be one or two randomers walking in silence and all of a sudden one will stop roll on the ground and yell they are craving something bizarre like kleenex. It doesn't matter how many people there are around they just do it, it's not attention seeking and it's not retarded, it's true randomness. Another example is a group of people will be talking about something semi-serious like clothes or grades and a randomer will pop in and yell a remark in a different language about donkeys or roof shingles. Randomers dress however they please, from pink and yellow to a brown shirt and orange pants, they are not colour co-ordinated and don't give a damn. Hopefully I've given you an idea of what a randomer is, remember they aren't retarded or attention seeking, they're USB MODE avec el padre.