What is this?

From a dictionary definition:

noun

• a shaped piece of fabric attached inside or outside a garment and forming a pouch used especially for carrying small articles.
• a bag or pouch.

adjective

• small enough or suitable for carrying in the pocket: a pocket watch.
• relatively small;
• smaller than usual: a pocket war;
• a pocket country.

verb (used with object)

• to put into one’s pocket: to pocket one’s keys.
• to take possession of as one’s own, often dishonestly: to pocket public funds.
• to submit to or endure without protest or open resentment: to pocket an insult.
• to conceal or suppress: to pocket one’s pride.
• to enclose or confine in or as if in a pocket: The town was pocketed in a small valley.
• Billiards, Pool. to drive (a ball) into a pocket.
• pocket-veto.
• to hem in (a contestant) so as to impede progress, as in racing.

We’ll start off with small or concealed for now.