bound
boundary
extremity
Moho
Mohorovicic discontinuity
Rubicon
Shoreline
border
borderline
boundary line
bourn
bourne
city line
county line
delimitation
demarcation
demarcation line
district line
edge
end
frontier
hairline
heliopause
limit
lineation
mete
outline
surface
Rounds
abounds
astounds
compounds
confounds
expounds
grounds
hounds
impounds
lbs
mounds
pounds
rounds
sounds
surrounds
zounds