Onomatopoeic word describing someone feeble, tottering, or decrepit (often used of elderly people who walk unsteadily).
祖父は足が弱くなって、最近はよぼよぼ歩いている。
My grandfather's legs have gotten weak, and lately he's been walking unsteadily.
冷たい風にさらされて、よぼよぼの犬が震えていた。
A frail old dog was trembling in the cold wind.
年を取るとよぼよぼになることもあるが、元気な人も多い。
People can become frail with age, but there are also many who stay vigorous.