Pocket/ˈpɑːkɪt/ Definition 1 of 6Pro Tip 1/3Variety in Size Pockets come in different sizes. Some can fit only a coin, others much more. Her jacket had tiny pockets, barely enough for a key. Pro Tip 2/3Hidden Space Pockets may be inside clothing, not visible from outside. He found a hidden pocket inside his travel bag. Pro Tip 3/3Secrecy Pockets can imply privacy or concealment. Something in your pocket is personal. She whispered and slipped a note into my pocket secretly.