What does undependable mean?
Undependable means unable to be trusted or relied upon. It describes people, machines, systems, claims, and conditions whose behaviour or quality cannot be predicted with confidence. The term is especially common for transport, weather, equipment, testimony, and other sources of assistance that may fail or vary without warning. An undependable colleague might miss important commitments; an undependable vehicle might break down repeatedly; and undependable evidence might conflict with other findings. The word is more explicit than simply describing something as doubtful or weak, because it identifies a recurring failure to meet expectations or a general lack of reliability. Although usable in everyday conversation, it also appears in professional assessments, reports, and formal criticism. In a general sense, undependable is the opposite of dependable, but it can carry the additional connotation of inconsistency: the person or thing may work well on some occasions while remaining impossible to count on over time.
adjectiveUnable to be trusted or relied upon to work, behave, or perform consistently.
- Not dependable; unable to be trusted or relied upon to perform consistently.
"Given the undependable weather, we postponed the excursion until conditions improved."
"The old car was so undependable that they stopped taking it on long journeys."
"Because the witness gave an undependable account, the journalist sought independent confirmation."
An undependable option is worse than no option at all: it promises reliability while refusing to deliver it.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does undependable come from?
Undependable was formed in English from the prefix un-, the base depend, and the suffix -able. Depend comes through Old French from Latin dependere, meaning “to hang down” and, by extension, “to rest on” or “to rely upon.” The formation follows the same Latin-based vocabulary that produced dependable, dependence, and dependent, while the un- prefix reverses the idea of being able to be relied upon.
Related word forms
How undependable is actually used
The word is used in formal, professional, and everyday registers. It often conveys a stronger sense than merely occasional unreliability, suggesting that the person or thing repeatedly fails, behaves inconsistently, or cannot be counted upon.
Easily confused with undependable
A dependable person or thing can be trusted to be reliable, whereas an undependable one cannot.