Rapaciously is how a rapacious person or company acts: they take in a grabbing, never-enough way, wanting more money, goods, or land than they need or have a right to. It tells you about the manner, not the speed. The meeting ended rapidly means it ended fast; they bought shops rapaciously means they kept seizing more than they should. You will meet the adverb in serious writing more than in speech. Friends would probably say they just kept taking. Though actually, it is not common even in newspapers; the adjective rapacious does more of the work. Use this form when you need to describe the taking as it happens.

貪婪地、掠奪成性地