Lacing is an unusual sexual perversion in which a man ejaculates into the food of unsuspecting people. The lacer gets sexual gratification from watching people unknowingly swallowing his semen.
After lacing the hot fudge, Stewart watched in silence while his neighbor's daughter devoured every bite of her ice cream.
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.