1. Noun: In pool, a natural is an easy shot requiring no side spin (english).
2. Adjective: In pool, a shot is said to be natural if it does not require adjustments, such as a cut angle, side spin , or unusual force. A natural bank shot , for example, is one in which simply shooting straight into the object ball at medium speed and with no spin will send the object ball directly into the target pocket on the other side of the table.
3. In three cushion billiards , the most standard shot where the third ball is advantageously placed in a corner.