Philandering: Sexual fooling around.
Philtrum: The vertical groove between the upper lip and the nose.
"Especially if there was philately going on."Within five lines, the author uses philately, philandering and philtrum. I can see him staring at one dictionary page and challenging himself to use three words from that page.
"That'd be philandering," Lucas said. "Philately is stamp-collecting."
"That's what I meant - stamp-collecting."
Lucas scrubbed an index finger across his philtrum.