An implied unilateral contract, also known as an implied-in-fact contract, is a legal agreement in which the parties involved do not explicitly state the terms and conditions of the contract. Instead, the terms and conditions of the contract are implied through the actions and behavior of the parties involved.

In simpler terms, this type of contract is based on the actions and behavior of the parties involved rather than a written or spoken agreement. The contract is created when one party performs an action or service, and the other party accepts the benefits of that action or service.

For example, if you hire a plumber to fix a leak in your home and they complete the work, you are expected to pay for their services. This is an example of an implied unilateral contract because the terms and conditions of the contract were not explicitly stated, but it was implied through the actions of the parties involved.

Implied unilateral contracts are often used in situations where it would be impractical or impossible to create a written contract. For example, when someone performs an act of kindness or performs a service without expectation of payment, an implied unilateral contract may be created when the other party accepts the benefits of that action or service.

However, there are some limitations to implied unilateral contracts. For instance, if the parties involved have a pre-existing relationship, such as a landlord and tenant, an implied unilateral contract may not be enforceable since the parties have an existing legal relationship.

Overall, an implied unilateral contract can be a useful legal tool in situations where a written or spoken agreement is not necessary or practical. However, it is important to understand the limitations and requirements for creating an enforceable implied unilateral contract.