Power or strength, protectiveness, or a feeling of overwhelm or of things being out of control, among other meanings. For more clues, look at what the large object or person represents. The big size may just represent "a greater amount" or "an extreme" of whatever the object or person represents. For example, if a flower represents love, a huge flower might represent huge feelings of love or adoration. If a car represents personal power, then an oversized car might represent an enhanced or exaggerated feeling of personal power.