As adjectives the difference between frail and fallible
is that
frail is easily broken; mentally or physically fragile; not firm or durable; liable to fail and perish; easily destroyed; not tenacious of life; weak; infirm while
fallible is capable of making mistakes or being wrong.
As a noun frail
is a basket made of rushes, used chiefly for containing figs and raisins.
As a verb frail
is to play a stringed instrument, usually a banjo, by picking with the back of a fingernail.