Modifiers matching obstruction:

• underground,
• movable,
• physical,
• permanent,
• isolated,
• topical,
• removable,
• subsurface,
• fixed,
• layer,
• additional,
• temporary,
• solid,
• vertical,
• opaque,
• overhead,
• taller,
• simple,
• current,
• smaller,
• significant,
• lateral,
• nearby,
• external,
• lighted,
• natural,
• artificial,
• past,
• visible,
• over,
• visual,
• common,
• virtual,
• local,
• relevant,
• major,
• horizontal,
• up,
• metal,
• underwater,
• indoor,
• electrical,
• low,
• immovable,
• larger,
• hard,
• hazardous,
• spatial,
• unusual,
• large,
• clear,
• environmental,
• structural,
• short,
• geographic,
• under,
• bigger,
• urethral,
• rigid,
• nasal,
• raised,
• terrestrial,
• outdoor,
• insurmountable,
• level,
• featureless,
• linear,
• internal,
• minor,
• hidden,
• cooler,
• adjacent,
• small,
• impenetrable,
• irregular,
• multiple,
• tall,
• typical,
• dense,
• hydraulic,
• surrounding,
• upright,
• discrete,
• mechanical,
• elongated,

Simple categories matching underground:

• topic,
• structure,
• area,
• reservoir,
• obstacle,
• installation,
• container,
• vegetable,
• item,
• housing,
• pipe,
• shelter,
• facility,
• fixture,
• group,
• location,
• stem,
• activity,
• system,
• world,
• object,
• tunnel,
• treasure,
• relic,
• supply,
• part,
• plant,
• material,
• formation,
• feature,
• cavity,
• opening,
• service,
• room,
• hydrocarbon,
• liquid,
• storage,
• harvester,
• construction,
• pest,
• space,
• void,
• resource,
• band,
• cable,
• fluid,
• property,
• line,
• cistern,
• pipeline,
• expanse,
• works,
• wealth,
• music,
• tank,
• equipment,
• work,
• development,
• fortification,
• conduit,
• duct,
• life,
• place,
• passage,
• cave,
• improvement,
• aquifer,
• utility,
• cavern,
• excavation,
• obstruction,
• enclosure,
• bunker,
• building,
• conductor,
• organ,