intrusive

Intrusive describes something that intrudes into a space or process, often without invitation or consent. The term is used in several domains to denote a boundary-crossing or insertion that is perceived as disruptive or inappropriate.

In geology, intrusive igneous rocks form when magma cools and crystallizes below the Earth's surface, producing coarse-grained textures. They contrast with extrusive rocks, which erupt onto the surface and cool rapidly to form fine grains. Common intrusive formations include plutons such as batholiths, and smaller features like dikes and sills that intrude through surrounding rock. The slow cooling beneath the surface yields large crystals.

In psychology, intrusive thoughts are unwanted, involuntary thoughts, images, or impulses that cause distress. They are commonly associated with anxiety disorders and obsessive-compulsive disorder. Treatments include cognitive-behavioral therapy, exposure and response prevention, and, in some cases, medication.

In everyday use, intrusive behavior describes actions that invade another's privacy or personal boundaries, such as prying questions or unsolicited interruptions. Social norms discourage such conduct, and responses may include setting explicit boundaries or limiting contact.

In linguistics, intrusive can describe a process where an extra sound is inserted at a word boundary to ease pronunciation, known as intrusive linking in some dialects. This is a descriptive term reflecting speech patterns rather than a value judgment.