To behave as though attracted to or trying to attract someone.

One who has a mania for music.

A person who is innocently overly friendly, especially the type of friendliness that is interpeted as seduction. Actions may include: giving away number, blowing kisses, caressing, and free lapdances. Also see Angelica.

anything someone does to get the attention of someone they like.

Verb definitions:-

1. To intentionally behave in a way that one believes will induce sexual arousal in their target. This word is distinct from 'tease' in two respects - firstly, it doesn't imply that the subject does not intend to satisfy the sexual arousal that he or she has manufactured and secondly, whereas the verb 'to tease' is usually used in reference to a woman's actions, the verb 'to flirt' can be used in reference to a man or a woman's actions.

2. To toy with (an idea usually, but sometimes an entity.)

Noun definition:-

One who is known to indulge in the actions detailed in the first verb definition can be described as 'a flirt'.

messing with a boy/girl because, a. you like them, b. you're trying to make someone else jealous, c.you're bored of your boyfriend/girlfriend, d. you're a stupid slut, e. you cant help yourself

this is a difficult word to define because what may be flirting to one person may not be to another. i guess, as a verb, it would be defined as intentionally trying to attract the attention of one you "like" using means that could be considered seductive.