Refers to a person who is strutting or "working it." The person who's "gettin' it" can be either male or female.
(Early morning in a school gym
Student 1: Those kids are getting loud they better quiet down before a teacher yells at them.
(teacher walks across the gym floor to the loud students)
Student 2: There's the teacher.
Student 1: Look at her... she's gettin' it!