(s)unaccented, light, weak(used of vowels or syllables) pronounced with little or no stress“a syllable that ends in a short vowel is a light syllable”, “a weak stress on the second syllable”
(s)fallible, frail, imperfect, weakwanting in moral strength, courage, or will; having the attributes of man as opposed to e.g. divine beings“I'm only a fallible human”, “frail humanity”
(s)faint, weakdeficient in magnitude; barely perceptible; lacking clarity or brightness or loudness etc“a faint outline”, “the wan sun cast faint shadows”, “the faint light of a distant candle”, “weak colors”, “a faint hissing sound”, “a faint aroma”, “a weak pulse”