in my recovery i had a true slip....my husband, daughter and i went to my home town for my 20 yr high school reunion. we were at a get together, and i reached back and grabbed what i thought was my drink - a coca cola on ice - and took a sip....turns out it was somebody else's watered down bloody mary. i knew immediately that was not my drink, but didn't have a place to spit it out. i returned the wrong drink to the table, made sure i had mine firmly in hand and that was that.
imho, that is a slip. a moment where you ingest or partake without realizing or planning what you are doing.
ANYTHING else is a planned relapse. a return to a prior state. thought before action.