The noun energy has 6 senses (first 4 from tagged texts)
1. (86) energy -- ((physics) the capacity of a physical system to do work; the units of energy are joules or ergs; "energy can take a wide variety of forms")
2. (8) energy, vigor, vigour, zip -- (forceful exertion; "he plays tennis with great energy"; "he's full of zip")
3. (6) energy, push, get-up-and-go -- (enterprising or ambitious drive; "Europeans often laugh at American energy")
4. (2) energy, muscularity, vigor, vigour, vim -- (an imaginative lively style (especially style of writing); "his writing conveys great energy"; "a remarkable muscularity of style")
5. energy, vim, vitality -- (a healthy capacity for vigorous activity; "jogging works off my excess energy"; "he seemed full of vim and vigor")
6. Department of Energy, Energy Department, Energy, DOE -- (the federal department responsible for maintaining a national energy policy of the United States; created in 1977)