Answer:
To save, to recycle.
To 'salvage gum' means to eat gum that has been thrown away or stuck under the desk (icky I know, but that's what it means)
'Salvage' also has a unique meaning in the Philippines where it takes a more macabre twist. Salvage there means an extrajudicial killing (cops or the military killing suspected criminals without the benefit of legal proceedings) or an assassination.
It's a pidgin anglicization of the Spanish word 'Salvaje' (Wild animal, feral), which when used as a verb means 'to maul'. It is still used as both an adjective/adverb and a verb in the Philippines in it's tagalog form 'Salbahe'.
The correct English equivalent would have been 'Savage' from the French word 'Sauvage'.