A definition from the Cambridge English Dictionary:
generation noun (AGE GROUP)
B1 [ C, + sing/pl verb ] all the people of about the same age within a society or within aparticular family:
B2 [ C, + sing/pl verb ] a period of about 25 to 30 years, in which most human babiesbecome adults and have their own children:
generation noun (AGE GROUP)
B1 [ C, + sing/pl verb ] all the people of about the same age within a society or within aparticular family: