Noah Webster's New International Dictionary of the English Language

1. (v. i.) To enter without invitation, permission, or welcome; to encroach; to trespass; as, to intrude on families at unseasonable hours; to intrude on the lands of another.

2. (v. t.) To thrust or force (something) in or upon; especially, to force (one's self) in without leave or welcome; as, to intrude one's presence into a conference; to intrude one's opinions upon another.

3. (v. t.) To enter by force; to invade.

4. (n.) The cause to enter or force a way, as into the crevices of rocks.