When you get the time, I would recommend as a reference the Oxford English Dictionary, the unabridged 20-something volume, which can be found at most public libraries. It's a good reference because the different definitions generally go in order from oldest to most recent, which enables you to trace how the meaning evolves. It also gives dated quotes from various sources to show how the word was used in sentences at different times.
And in the meantime, I suggest looking at the Constition online, here, for example, and doing a find-on-page search for the word "several", which appears "several" times throughout the document. And each time you see it, pretend the word isn't there, and ask yourself how that would possibly affect the meaning of the sentence you're looking at. Remember that the drafters of the document generally didn't waste words unnecessarily.