anything really! it can mean anything! the word fresh really compliments the use of the word units as well..see example below!
1.) " hey, those (shoes) units are really fresh, yo!
2.) " wow, things are really de-freshing today...we need 100 CC's of units"
3.) (using the term to describe a good time) "This party is really unit fresh."
Person A:"Hey man, I really like hanging out with you."
Person B: "Ya, for sure. Units are here."