undergrounds
词形变化：
动词过去式: undergrounded | 动词过去分词: undergrounded | 动词现在分词: undergrounding | 动词第三人称单数: undergrounds |
同义词：
covert | concealed | belowground | secret | undercover | surreptitious | clandestine | hush-hush | subway | resistance | tube | metro | subterranean | subterrestrial | hypogeous | sunken | subversive | nether | buried | secretive | below the surface | dissident | underfoot | alternative | hidden | underhand | underhanded | backdoor | under-the-table | under-the-counter | under wraps | private | opposition | subversiveness | incendiaries | terrorists | underground railway | subterraneously | subterraneanly | by tube | secretly | in secret | privately | in private | out of view | covertly | clandestinely | surreptitiously | furtively | stealthily | on the sly | sneakily | sneakingly | underhandedly | illegally | unlawfully | underworld | cloak-and-dagger | hell | nether regions | tunnel | underpass | gallery | hole-and-corner | corridor | subterrane | mine | hugger-mugger | cave | burrow | subway system | hole | pit | grave | tomb | sepulchre | crypt | vault |
反义词：