lackingEnglishOxford American Thesauruslacking adjective 1 proof was lacking: absent, missing, nonexistent, not present, unavailable, not to be found. ▷antonyms present, plentiful. 2 the advocate general found the government lacking on two counts: deficient, defective, inadequate, wanting, limited, flawed, faulty, insufficient, unacceptable, impaired, imperfect, second-rate, restricted, inferior. ▷antonyms perfect. 3 the game was lacking in atmosphere: without, devoid of, bereft of, bankrupt of, destitute of, empty of, deprived of, free from/of; deficient in, low on, short on, in need of; informal minus. ▷antonyms full of.