Complex sentence: Underbucking is a type of log bucking where the cuts are made upwards from the lower side of a suspended log, as opposed to "overbucking", cutting from the top side down.
Split into simpler sentences: Underbucking is a type of log bucking where the cuts are made upwards from the lower side of a suspended log. It is the opposite of "overbucking", cutting from the top side down.