unstable
unsteady
Lissajous figure
alternation
ambling
ambulation
anile
back-and-forth
backpacking
cautious
circumspect
claudicant
collapsing
coming and going
crabbed
crawling
creeping
creeping like snail
debilitated
deciduous
declining
declivitous
decrepit
decurrent
deliberate
descendant
descending
dilapidated
doddered
doddering
doddery
down
down-reaching
downcoming
downfalling
downgoing
downhill
downsinking
downward
drooping
dropping
easy
ebb and flow
falling
faltering
feeble
flagging
fluctuation
flux and reflux
foot-dragging
footing
footing it
firm