Lissajous figure
alternation
back-and-forth
coming and going
dilapidated
doddering
ebb and flow
fluctuation
flux and reflux
groggy
oscillation
pendulation
ramshackle
reciprocation
rhythmic play
ricketish
rickety
rocky
seesaw
seesawing
shaky
shifting
shuffling
sine wave
spidery
spindly
teeter
teeter-totter
teeter-tottering
teetery
to-and-fro
tottering
tottery
tumbledown
unsteady
ups and downs
vacillation
variation
vicissitude
wavering
wigwag
wobbly
metering
petering