Playin is a slang word for playing. For example: I was just playin around. Also used as an easy hash tag word #playin. The work "playin" is used in may songs and rap songs since it is easier to rhyme with.
Did you have fun on TikToktoday? Yes I was playin around on it all day. #Playin
The act of hitting on or flirting with a group of females that you know it's impossible to strike out with.
Guy 1: How'd it go with those hoes last night homie?
Guy 2: Good, man I was playin' T-Ball so you know I went home and knocked three different girls out of the park.