If you’re a poker player, when you “cull” the cards you have selected a bunch of good cards and arranged to deal them to yourself or someone you want to win. (That’s cheating, by the way.) But if you’re a cowboy, when you ride out to “cull” the herd, you’re looking for the sick or weak animals to cut out.
In other words, “culling” can mean taking out the good (the cards that will help you win) or the bad (the cows that are sick). But “culling” can also have a totally neutral meaning: to choose or collect. (“Cull” is from the Latin colligere, which also gave us “collect.”)
Dictionaries merely muddy the waters. In Webster’s New World College Dictionary (the one used by most news publications), the first definition of “cull” is “to pick out; select
The American Heritage Dictionary of the English Language is perfectly neutral: “to pick out from others; select,” as is the Random House Webster’s Unabridged Dictionary.
Context will often give the clue whether “cull” is being used as positive, negative or neutral. “She had to cull hours of film clips to get the ones she wanted,” for example, is pretty clear. But “he culled his book collection by a third” doesn’t tell you whether he kept one-third or two-thirds. So if you’re aware that some people think of the word as negative and others think of it as positive, you can avoid wrong impressions.
As a noun, however, “cull” has no such identity crisis. It means the leftovers, the inferior stuff, the detritus that results from culling. It’s always negative.
OK, in poker, the “cull” will probably be positive, but only if you don’t get caught.