Contact

Part of speech: noun (n.)

1. A close union or junction of bodies; a touching or meeting.

2. The property of two curves, or surfaces, which meet, and at the point of meeting have a common direction.

3. The plane between two adjacent bodies of dissimilar rock. Raymond. Contact level, a delicate level so pivoted as to tilt when two parts of a measuring apparatus come into contact with each other; -- used in precise determinations of lengths and in the accurate graduation of instruments.