From Rap Dictionary
- In hip-hop parlance, the term refers to something like a jam session in which everyone contributes to the creative experience. Be they DJs, dancers, rappers or graffiti writers, all the different artists that collectively make up the culture of hip-hop can have their own cypher. When dancers cypher, you’ll see each taking a turn in the center of a circle, contributing a unique style, then resting. The center of circle is never empty and the energy of the cypher grows as the dancers push themselves into increasing levels of athleticism. Rappers cypher together huddled in a corner, rhyming a capella to handclaps or any ambient beats in the surrounding environment. "I was walkin' down the street about three o'clock, when I saw another MC at the end of the block, talkin' to kids tellin' em, how they had to get the dough, so I rolled right up in the cipher and said 'Yo!'" -- K-Os (Freeze ) 
- A pot-smoking session, or rotation. "yo can i get in on this cipher?"