Yes, you can define verses precisely. The Metamorphoses are written in dactylic hexameter, and so each line is constructed with the same rules.
You can check the line numbers for yourself on PHI or Perseus, but you'll get a slight discrepancy. The text as it has come down in manuscripts included some spurious interpolations that were included in the Middle Ages (and which probably originated as marginalia). The text on PHI includes the numbering but removes the spurious verses, while Perseus renumbered everything.
If you're counting the numbered lines on PHI, you'll end up with 11,995.
1: 779 lines
2: 875
3: 733
4: 803
5: 678
6: 721
7: 865
8: 884
9: 797
10: 739
11: 795
12: 628
13: 968
14: 851
15: 879
But the number will be off slightly if you're counting actual lines present. In the first book, for example, if you go to the last page, you'll see that the highest number is 775 (it provides every fifth line so that you can quickly find a line) with four additional lines afterward, giving you 779. But if you go back a few pages, you'll see that line 546 has been excised.
There is some debate over which lines are authentic and which are not. Moreover, the text as we have it is reconstructed from a variety of manuscripts, and not all manuscripts have all the interpolated lines.
A more accurate statement for Wikipedia would be that the Metamorphoses comes down to us in about 11,995 lines, and some of those lines might be inauthentic additions added to the text at a later date.
