To be extremely intoxicated by the ingestion of one or more substances, such that the senses become acutely imbalanced and hallucination has become the norm.
Portmanteau derived from the concept of eigenvalues (/eigenvectors) in mathematics by which the axis of highest variation can be found in multidimensional data, and being faced, or intoxicated beyond the norm.
"Last night I was more wankered than the time I thought the walls were made of camembert. In fact, I was eigenfaced!" Conceded the Bishop, before collapsing. (Rumsblatt, 1925)
Heavily intoxicated by a chemical substance (esp. alcohol).
Oh my god, I can't believe how eigenfaced I was last night!