Ipsilateral: adjective; on the same side of.
Used in descriptions of how two anatomical or pathological structures are related.
1. “a lesion of the facial nerve produces ipsilateral facial weakness” means that an injury to the facial nerve produces weakness in the muscles of the face on the same side as the injury.
2. “the dorsal columns carry ipsilateral sensory fibers” means that the nerve fibers traveling in the part of the spinal cord known as the dorsal columns carry sensory information from the same side of the body; so the dorsal columns on the right carry information from the right side of the body and the dorsal columns on the left carry information from the left side of the body.
See for comparison: contralateral.