ˌfibəˈnächē-, ˌfēb- noun
Usage: usually capitalized F
Etymology: after Leonardo Fibonacci (Leonardo Pisano) died ab 1250 Italian mathematician
: a number in the infinite sequence 1, 1, 2, 3, 5, 8, 13, … of which the first two terms are 1 and 1 and each succeeding term is the sum of the two immediately preceding