Thinline Fender Telecasters are so-called because they are thinner than standard Telecasters, ie. the body is "comfort contoured" (Fenderese for material cut out of the back) like the Stratocaster.

Gibson make/made thin versions of some guitars, notably their hollow-bodied jazz guitars, which are designated by a "T" after the model number. I've only ever seen one accoustic (an L5T), but there are plenty of examples of semi-accoustic electrics, and some of these were/are standard models, eg. the ES175T. Dealers often use the word thinline to describe such guitars, but I've never seen Gibson do it.