Ambrosia, as we all know, is the food of the gods and its derivation is obvious at first glance. It comes from the Greek α-βροτος = not mortal or immortal. However it would seem that this derivation and meaning is disputed. I have examples below that show that ambrosia is applied to more things than food. This is what Leaf (or Bayfield) has to say about it in my edition of the Iliad edited by Leaf and Bayfield.
“ἀμβρόσιος: delicious. The idea of fragrance is always suitable to the idea of ἀμβρόσιος. While there is no clear instance of it meaning immortal only, the word is probably not pure Greek at all but borrowed from the Semitic ambar, ambergris, the famous perfume to which the Orientals assign mythical miraculous properties. There are two words ἃμβροτος, one meaning immortal ( α, βροτος); the other a by-form of ἀμβρόσιος. Their similarity in sound is a mere accident. The restriction of ἀμβρόσιος and ἄμβροτος, fragrant, to divine objects is due to a false popular identification of the words with ἄμβροτος mortal.”
Wikipaedia gives a competely different derivation (http://en.wikipedia.org/wiki/Ambrosia)
“The concept of an immortality drink is attested in at least two Indo-European areas: Greek and Sanskrit. The Greek ἀμβροσία (ambrosia) is semantically linked to the Sanskrit अमृत(amṛta) as both words denote a drink or food that gods use to achieve immortality. The two words appear to be derived from the same Indo-European form *ṇ-mṛ-to-, “immortal” (n-: negative prefix from which the prefix a- in both Greek and Sanskrit are derived; mṛ: zero grade of *mer-, “to die”; and -to-: adjectival suffix).”
For myself, what ever the derivation, the word conjures up fragrant smells such as you might catch on a warm summer’s evening from honeysuckle or other sweet smelling plants.
Here are a few examples of ambrosia, mostly from Homer.
The gods eat ambrosia and drink nectar. for example in the Odyssey Calypso prepares a meal for Hermes
ὥς ἄρα φωνήσασα θεὰ παρέθηκε τράπεζαν
ἀμβροσίης πλήσασα, κέρασσε δὲ νέκταρ ἐρυθρόν.
So saying the goddess put a table before him filling it with ambrosia and she mixed the red nectar.
Even the god’s horses eat ambrosia
ἔνθ᾽ ἵππους ἔστησε θεὰ λευκώλενος Ἥρη
λύσασ᾽ ἐξ ὀχέων, περὶ δ᾽ ἠέρα πουλὺν ἔχευε:
τοῖσιν δ᾽ ἀμβροσίην Σιμόεις ἀνέτειλε νέμεσθαι.
White-armed Hera stood the horses there, releasing them from the chariot, and she poured around a thick mist. Simois ordered ambrosia to come up for them to graze.
Sometimes the gods drink ambrosia rather then eat it.
Κῆ δ᾽ ἀμβροσίας μὲν κράτηρ ἐκέκρατο,
᾽Ερμᾶς δ᾽ ἔλεν ὄλπιν θέοισ οἰνοχόησαι.
κῆνοι δ᾽ ἄπα πάντες καρχήσια τ᾽ ἦχον
κάλειβον ἀράσαντο δὲ πάμπαν ἔσλα
And there the bowl of ambrosia was mixed and Hermes took the ladle to pour out for the gods; and then all held goblets and made libation, and wished good fortune to the bridegroom.
Sappho fragment 47
But ambrosia is not just confined to food. Sometimes the night is called ambrosial. So Hermes says to Priam
πῇ πάτερ ὧδ᾽ ἵππους τε καὶ ἡμιόνους ἰθύνεις
νύκτα δι᾽ ἀμβροσίην, ὅτε θ᾽ εὕδουσι βροτοὶ ἄλλοι;
Where, father, are you directing your horses and mules, through the ambrosial night, when other mortals are sleeping?
Iliad 24 363
And before that Hermes had put on his beautiful golden ambrosial sandals.
καλὰ πέδιλα ἀμβρόσια χρύσεια
Iliad 24 339