Blowjob
Blowjob is a colloquial term for oral sex performed on a penis. The word is not BDSM-specific and is used generally. The more formal term is fellatio. It refers to stimulating the penis with the mouth, lips and tongue.
The term is used in many sexual contexts, including outside the BDSM scene. It is important that oral sex is consensual and carried out with basic hygiene in mind. Care should be taken to avoid using teeth or too much pressure, as this can cause pain or injury. Sexually transmitted infections should also be considered.