Singular. Plural form may not exist.
Related to both Hippy and Gypsy terminology in connotation.
1. An individual in approval of environmental, spiritual, animal, and humanity concerns who approves of peaceful negotiation, but will resort to violence if deemed necessary.
2. One who is bound only by personal ethics, which are not the same to another, but is commonly libertarian in their political beliefs, and may be neutral but not pro the extinguish of any "life" form.
3. Someone who will read your palm, punch you in the face, and hug a tree all at the same time.
4. (uncommon) Referring to a person who has ties with many different types of social circles, combined with one or more of the above definitions, who seems dangerous.
Whoa dude! Don't cross that bitch- she's a hypsie.
You know what they say about crossing a hypsie- bug one, and find several different cliques at your throat.
Oh, they go by the hypsie mentality- 'If it doesn't harm anyone unless they request it, and you don't fuck with me, do what you like.' But what they really mean is- fuck with what I care about and it'll come back to you!!