Purists will tell you that a true macro lens gives you at least a 1:1 life size image on the sensor or negative, though hardcore pedants (like me, obviously) might point out that when the term 'photo-macrograph' was originally coined, it just indicated a close-up photo taken without attaching your camera to a microscope ('photo-micrography'), and therefore of lower magnification (though no specific magnification on the negative seems to have been specified). A lot of mid-range zooms (especially from the film era) have a macro feature. It's not something I'd avoid; the manufacturers knew they'd mostly be used as general purpose zooms, with macro just a useful extra, and designed them accordingly. Some gave very high quality images at normal distances by the standards of the time. Magnification rarely went further than 'semi-Macro' 1:2 (e.g. the Nikon 28-105 at the long end, which has a special macro switch like Chris's Tamron), and was often less. One exception is Nikon's 70-180 zoom, which was part of their 'Micro' range (Nikon's confusing term for macro), and designed primarily but not exclusively for macro work (it goes to 1:1.32).
. (cynical hat off). 
