navel, belly button, protrusion or depression in the middle of an object...

navel piercing, belly button ring

lower abdomen

secret savings, secret stash, money hidden away

umbilical cord

peccary

navel, belly button

protruding navel, outie

belly-button lint, navel fluff

umbilical cord

perverseness, perversity, perverse person...

secret savings, secret stash, money hidden away

navel piercing, belly button ring

bitter regret

fulcrum peg (fitted into the cavity in an oar as part of a traditional oarlock)

fulcrum peg (fitted into the cavity in an oar as part of a traditional oarlock)

circumference of the navel, treasure trail, sagittal hair

umbilical cord blood

navel orange

umbilical artery

perverseness, perversity, perverse person...

to regret bitterly, to be very sorry (for), to bite one's navel

to regret bitterly, to be very sorry (for), to bite one's navel

umbilical hernia

fur seal (esp. the northern fur seal, Callorhinus ursinus), Alaskan fur seal

secret savings

to (go into a) sulk, to get cranky, to get cross...

to make up one's mind (to do something), to resolve firmly (to do something)

pit of the stomach

umbilical vein