Someone who repeatedly promises to do something but does not complete it may be described as unreliable, inconsistent, undependable, flaky, or as someone who doesn’t follow through. The right term depends on whether the issue is occasional, habitual, or deliberate.
Which Term Fits the Pattern?
- General repeated failure to follow through: Unreliable
- Behavior varies from one occasion to another: Inconsistent
- Cannot be depended on to complete commitments: Undependable
- Casual plans and social commitments: Flaky
Unreliable
The broadest and most natural adjective for someone you cannot consistently depend on.
Example: “He’s unreliable when it comes to meeting deadlines.”
Inconsistent
Best when the person sometimes follows through and sometimes does not.
Example: “Her work is good, but she can be inconsistent about finishing tasks on time.”
Undependable
Close to unreliable and slightly more formal.
Example: “The supplier became undependable after several missed deliveries.”
Flaky
Informal and common for someone who cancels, changes plans, or fails to do what they said they would do.
Example: “He’s fun to be around, but he can be flaky about actually showing up.”
Uncommitted
Best when the problem appears to be lack of commitment rather than inability.
Example: “The project struggled because several members seemed uncommitted.”
All talk
Informal phrase for someone who talks enthusiastically about what they will do but rarely acts.
Example: “He keeps promising to help, but so far it’s been all talk.”
Doesn’t follow through
Plain and behavior-focused, often better than attaching a label to the person.
Example: “She has good ideas but doesn’t always follow through on them.”
Fails to deliver
Professional and outcome-focused, especially for work, services, or promises.
Example: “The contractor repeatedly failed to deliver on the agreed milestones.”
Breaks commitments
Direct and stronger when the person has explicitly agreed to something and then does not do it.
Example: “The issue is not one missed meeting; it’s that he repeatedly breaks commitments.”
Doesn’t keep their word
Best when follow-through involves a promise rather than merely a task.
Example: “It’s hard to trust someone who consistently doesn’t keep their word.”
Unreliable vs. Inconsistent
Unreliable means you cannot depend on someone. Inconsistent means their behavior or performance varies. Someone can be inconsistent without being completely unreliable.
Describe the Behavior When Stakes Are High
At work or in a conflict, a factual description such as “three agreed deadlines were missed” is usually more useful than calling someone flaky or unreliable.