The full form of IYKWIM is “If You Know What I Mean”.

“If You Know What I Mean” is a song written and recorded by Neil Diamond. It is a track from Diamond’s 1976 album, Beautiful Noise, and was his third number one on the Easy Listening chart, where it spent two weeks. “If You Know What I Mean” went to number one for two nonconsecutive weeks and peaked at number eleven on the Billboard Hot 100. In Canada, the song reached number 19 on the pop singles chart and hit number one on the Adult Contemporary chart.

Billboard described “If You Know What I Mean” as a “powerful ballad,” stating that Diamond sings with more emotion than he had in the recent past, and also praising Robbie Robertson’s production.

Diamond has stated that the song is a “tender recollection” of a relationship in his teens, in which he successfully seduced a significantly older woman