• adjective. that might have been; unfulfilled: an actor manqué.
— ORIGIN French, from manquer ‘to lack’.
You know, the lookit-all-the-fancy-French-words-I-know-a
Rather than simply tagging on the rather cliché (see, I know some French too) manqué, in "lexicographer manqué," our pal Simon coulda taken it one step further and worked in a bit of a pun, in the form of "lexicographer manqueller." Now that would have been funny... if your nose were high enough in the air to catch the smarmy little play on words.
By the way, AskOxford (source for definition and pronunciation guide above) and InfoPlease.com don't seem to agree on the pronunciation for manqué.
Which is a completely different word, with a different pronunciation, than manque (without the little French thingie above the "e").
One more source: Dave's Colloquial (That Means "How Normal People Talk") Dictionary of Snobby Furrin Words
manqué (mang-kay), adj.: wannabe, i.e. author manqué = author wannabe.