PDA stands for public display of affection. If you and your significant other were having some fun in public, than that could be what you are accused of.
If you were accused of PDA, the reference was likely to a "public display of affection." Hugging, kissing, making out, groping and other activities generally reserved for private are often referred to as PDAs.
One meaning for PDA is "public display of affection." Perhaps you've been seen hugging or kissing or holding hands in a situation where some people object to this activity.
