The mantra at the end of the Heart Sutra:
GATE GATE PARAGATE PARASAMGATE BODHI SVAHA.
The key word is BODHI, a feminine noun in the vocative case, which means awakening. All the other words are also in the vocative feminine and therefore modify BODHI.
GATE means gone.
PARAGATE means gone to the further shore and is a stock Sanskrit expression used by Jains and Buddhists to refer to arahants. (The word PARA means the bank of a river opposite to the one on which one is presently standing.)
PARASAMGATE means completely gone to the further shore. (The prefix SAM is intensive in meaning: completely, thoroughly, altogether.)
SVAHA is an indeclinable particle from Vedic Sanskrit. It is said to be the name of the wife of Agni, the god of fire. It is used at the end of a recitation that accompanies a burnt offering made at a Vedic sacrifice (rather as "amen" is used at the end of a prayer in Christian liturgy). It cannot really be translated, since it is a performative word rather than a word that conveys meaning.
The whole mantra, literally translated, comes out a bit like this: "Oh awakening that has gone, gone, gone to the further shore, gone completely to the further shore. Amen."
More loosely translated, it means this: "You Brahmin priests with your fancy fire sacrifices aren't the only ones who get people to heaven. We can do it without killing animals and wasting trees. So there."
Allen Ginsberg's version:
"Gone gone totally gone totally gone over the top, wakened mind, So, ah!"