The ingress protection (IP) rating defines the sealing effectiveness of electrical enclosures against foreign particles like accidental contact, dust, moisture, liquids, etc. The rating is read as IP followed by 2 digits: the first digit, relating to protection against the ingress of solid particles(dust), and the second is the protection against the ingress of water.
Typically fixtures with a rating of IP65, 66 & 67 are considered IP waterproof ratings. For interior applications such as the bathroom, an IP rating of IP44 or IP65 is sufficient subject to the location the lamp is installed.