What are cowper's glands?

Cowper's glands are Accessory sex glands.
Cowper's glands are pea sized glands present inferior to the prostate gland in the male reproductive system. They produce thick clear mucus before ejaculation that drains into the spongy urethra.
The bulbourethral gland or Cowper's gland, which is homologous to the Bartholin's gland in females, produces a pre-ejaculate that cleanses and lubricates the urethra before the arrival of the semen.