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.