Spunk is a slang term for seminal fluid. It may also be used as a verb, meaning to ejaculate semen. Spunk is a thick white or opaque colored liquid made up of spermatozoa (sperm) and seminal plasma which helps keep the sperm alive. It is expelled from the urethra during orgasm.
As well as seminal fluid or semen, spunk is also known by other colloquial phrases such as Seed, Cum, Jizz, Jism, or Splooge.