Full contact describes massage in which the therapist's body, not her hands alone, meets the client's across broad areas; it is the defining condition of body-to-body.
Full contact is a measure of surface, not of intensity. In a spa treatment the contact at any moment is a hand or two and perhaps a forearm, with a towel draped over everything not being worked. In full contact the working surface is large and keeps changing shape: a forearm along the calf, a thigh across the hamstring, a torso along the spine. The term states how much of two bodies meet. It says nothing about how hard.
Temperature matters more. Broad contact moves heat quickly between skins, so a cool room is noticed within seconds and a warm one vanishes from attention. Turn the room heating up well before she arrives.
The medium matters more. A hand can work on dry skin for a minute; a torso cannot travel across it at all. Full contact depends on an unbroken film of oil, hence oil that goes on warm and is replenished as the session runs rather than applied once and forgotten.
Stillness matters more. With a wide surface, a pause is itself pressure: weight resting in one place spreads outward and sinks. Work built on full contact therefore has rests written into it, intervals without movement that belong to the technique as much as the passes do.
Because the contact is broad, the adjustment a client asks for is almost always about weight, not about reach. A single word, firmer or lighter, changes the angle she works at and so the load carried through it. The journal entry on what full contact covers goes further, and contour explains how a large surface is made to follow a curved one.