Feebleness/ˈfiːblnəs/ Definition 1 of 3Pro Tip 1/3Physical Weakness Describes severe lack of strength often due to illness or aging. After her illness, she felt an overwhelming feebleness. Pro Tip 2/3Lacking Energy Used for expressing severe tiredness or low energy levels. The feebleness he felt in the mornings made getting out of bed hard. Pro Tip 3/3Not Just Age While often related to old age, it can describe any temporary physical weakness. His feebleness was due to not eating properly.