【Voracious】 , 【gluttonous】 ,  【ravenous】 ,  【ravening】 ,  【rapacious】  can all mean excessively greedy and can all apply to persons, their appetites and reactions, or their behavior.

【Voracious】 implies habitual gorging with food or drink, or with whatever satisfies an excessive appetite.

【Gluttonous】  differs from  【voracious】 chiefly in its common suggestions of covetous delight (as in food) and of acquiring or eating past need or to the point of satiety.

【Ravenous】 implies excessive hunger and suggests violent or grasping methods of dealing with food or with whatever satisfies an appetite.

【Ravening】  is sometimes employed in place of  【ravenous】 , but more often it comes close to  【rapacious】 in suggesting a violent tendency to seize or appropriate to oneself in the manner of a bird of prey or a predatory animal.

【Rapacious】 may imply the seizure of food, but more often it suggests excessive and utterly selfish acquisitiveness or cupidity.