What is the meaning of pearl?

noun

• A smooth lustrous round structure inside the shell of a clam or oyster; much valued as a jewel.
• A shade of white the color of bleached bones.
  • synonyms: bone, ivory, off-white
• A shape that is spherical and small.
  • usage: "he studied the shapes of low-viscosity drops"; "beads of sweat on his forehead"
  • synonyms: drop, bead

verb

• Gather pearls, from oysters in the ocean. .