Slab (graded card)
A collectible sealed into a tamper-evident case by a third-party grading company, with an authenticated condition grade printed on the label.
A slab is a card, coin or comic that has been sent to a third-party grading company, authenticated, assessed for condition, and sealed into a rigid tamper-evident holder with a label showing the grade. The common graders in cards are PSA, BGS, CGC and SGC, and most grade on a 1 to 10 scale where 10 is the top. Sellers use slab, graded and encapsulated to mean the same thing.
The point of a slab is that it removes the argument. An ungraded card's condition is an opinion shared between a seller and a buyer looking at a phone screen. A graded card's condition is a number somebody independent already assigned. That is why slabs tend to sell faster on stream than raw cards of the same item, and usually for more.
Slabs are also easier to sell on camera, because the label does the talking: grade, year, set and player are all readable in one shot. Put those same details in the listing title. Buyers search for the grade as often as they search for the card.