is the word with 3 pairs of consecutive letters.
If you want to get a little esoteric (and a little disputed):
You can go one pair better than that! subbookkeeper
is the only word found in an English langauge dictionary with four pairs of double letters in a row. This word is in W2, but is not in W3 or OED2.
WOOLLOOMMOOLOO, according to the Australian Encyclopedia and various editions of Encyclopaedia Britannica, is the original spelling of Woolloomooloo, a suburb and bay in Sydney, Australia