gravity tremble: The variations in experienced gravity found aboard starships making use of the thrust gravity provided by nuclear pulse drives, or other discontinuous-thrust drives. Essentially, the gravity tremble refers to that portion of the thrust variation not damped out by the thrust transfer framework, leading to a predictable variation in experienced gravity around its nominal value, from the jarring on-off transitions of the earliest undamped concussion drives to the smooth and gentle oscillation (resembling a phugoid cycle) of modern fusion-pulse sail drives.
The term is also used to refer to the distinctive gait seen in long-term pulse-drive starship crewers (or, more accurately, crewers of those starships in which the pulse rate is relatively fast). With experience in maneuvering under trembling gravity, such crewers develop the habit of attuning their stride interval to the tremble frequency, pushing off and up with the drop and descending with the rise, thus gaining the most advantage from the momentarily lighter gravity.
– A Star Traveler’s Dictionary