A type of skimpy armor typically worn by an attractive female warrior in such a way as to maximize exposure to body parts such as cleavage, midriff, ass, legs etc. The top breast-covering portion either is a bikini top, or (more commonly) is often shaped very much like one but showing some obvious signs of metallic reinforcement. The bottom may be a bikini brief, a short or long loincloth, a skirt, full pants, or perhaps some combination. Armored boots and a cape can be expected, along with options such as helmets, gauntlets, elbow/knee pads, shoulder pads, power suit etc.
Naturally, the irony is that less coverage usually means less protection against attacks, so one assumes that bikini armor is inherently magical in nature (so as to apply inverse relationship between coverage and protection).