The preposition plus has long been used with a meaning equivalent to and (as in “two plus two”); people have come to use plus as a conjunction much like and. Sense 2 is considered to be an adverb by some. It is used chiefly in speech and in informal writing.
Examples of PLUS
He works a full-time job during the day, plus he goes to school at night.
I enjoy gardening, plus it's good exercise.
First Known Use of PLUS
Medical Definition of PLUS
: relating to or being a particular one of the two mating types that are required for successful fertilization in sexual reproduction in some lower plants (as a fungus)—compare minus