geometric series

WordReference Random House Unabridged Dictionary of American English © 2025

ge′omet′ric se′ries, [Math.]

1. Mathematics an infinite series of the form, c + cx + cx² + cx³ + …, where c and x are real numbers.
2. Mathematics See geometric progression. 

• 1830–40

Collins Concise English Dictionary © HarperCollins Publishers::

geometric series noun

1. a geometric progression written as a sum, as in 1 + 2 + 4 + 8