Definition of in- :
1. A prefix from Eng. prep. in, also from Lat. prep. in, meaning in, into, on, among; as, inbred, inborn, inroad; incline, inject, intrude. In words from the Latin, in- regularly becomes il- before l, ir- before r, and im- before a labial; as, illusion, irruption, imblue, immigrate, impart. In- is sometimes used with an simple intensive force.
2. An inseparable prefix, or particle, meaning not, non-, un- as, inactive, incapable, inapt. regularly becomes il- before l, ir- before r, and im- before a labial.
3. The specific signification of in is situation or place with respect to surrounding, environment, encompassment, etc. It is used with verbs signifying being, resting, or moving within limits, or within circumstances or conditions of any kind conceived of as limiting, confining, or investing, either wholly or in part. In its different applications, it approaches some of the meanings of, and sometimes is interchangeable with, within, into, on, at, of, and among.