"Does not happen!" -- pg. 73.
The author has Teppic using crampons to climb walls. I've seen this discussed about another author, and someone on a forum said they looked in the OED to find that crampon was an archaic word for a sort of piton. Maybe. I think Prachett should have gone with piton.
mutton avec no talking (pg. 93) -- It's french, means "with". Should have known this from the song lyric Voulez-vous coucher avec moi (ce soir)? from that Labelle song.
stack of wood licker wicker hurdles (pg. 50) -- On a Terry Prachett forum there is some discussion of this. Possibly a printer's error, in the Transworld edition the phrase is "wood like".
Obloquy (pg. 23) -- The condition of one that is discredited.
Dovecote (pg. 103) -- A small compartmented raised house or box for domestic pigeons.