underground

noun 0.688

undercroft

noun 0.658

basement

noun 0.633

storm cellar

noun 0.613

cellar

noun 0.601

underworld

noun 0.588

underpass

noun 0.588

oubliette

noun 0.588

subsurface

noun 0.584

hypogeum

noun 0.580

bunker

noun 0.567

subsoil

noun 0.565

cavern

noun 0.556

subfloor

noun 0.555

crawl space

noun 0.555

burrow

noun 0.550

tunnel

noun 0.550

underfloor

noun 0.547

air-raid shelter

noun 0.542

trench

noun 0.539

soakaway

noun 0.537

crawlway

noun 0.534

sewer

noun 0.533

cave

noun 0.532

dugout

noun 0.532

trencher

noun 0.531

underneath

noun 0.530

grotto

noun 0.530

subsoiler

noun 0.530

understory

noun 0.529

downstairs

noun 0.525

subgrade

noun 0.525

burial chamber

noun 0.525

souse

noun 0.525

lair

noun 0.523

ground floor

noun 0.516

soffit

noun 0.514

subway

noun 0.514

sinkhole

noun 0.511

sump

noun 0.511

cellarage

noun 0.510

rathole

noun 0.510

storm sewer

noun 0.510

bomb shelter

noun 0.509

wine cellar

noun 0.508

subbase

noun 0.507

keller

noun 0.505

culvert

noun 0.502

underfoot

noun 0.502

water tunnel

noun 0.502

substructure

noun 0.501

underlay

noun 0.501

solum

noun 0.500