Modern Dictionary:
RELIGION: a set of beliefs concerning the cause, nature and purpose of the Universe.
Websters Dictionary 1828
RELIGION: includes a belief in the being and perfection of God, in the Revelation of His will to man, in mans obligation to obey His commands, in a state of reward and punishments and in mans accountableness to God; and also true godliness or piety of life, with the practice of all moral duties.
The first definition is all encompassing of any group to define anything. If you rely on current dictionaries to understand the meaning of words you wont understand the intended meaning of our founding documents.