Heres some more info on the meaning of the title.
Originally, "Cloverfield" was reported to be nothing more than an early working title, derived from the name of a street that JJ Abrams has an office on or near.
More recently, "Cloverfield" director Matt Reeves explained in a USA Today article that - within the context of the story itself - "Cloverfield" is the codename of the military operation dispatched to battle the monster.
(Cloverfield, incidentally, is the name of the military operation to stop the monster, though that's not spelled out in the film.)
(This is - according to one theory - because the three-toed creature left giant clover-shaped footprints all over Manhattan, making it look like a "field of clover," which is as good an explanation as any, although not confirmed. There are many other interesting fan-created theories for the appellation, all with credible reasoning.)