pron

• (obsolete or rare) Himself, herself, itself, themselves; that specific (person mentioned).
  "This argument was put forward by the defendant self."
• (commercial or humorous) Myself.
  "I made out a cheque, payable to self, which cheered me up somewhat."

noun

• (botany) A seedling produced by self-pollination (plural selfs).
• (botany) A flower having its colour uniform as opposed to variegated.
• (molecular biology, immunology) Any molecule, cell, or tissue of an organism's own (belonging to the self), as opposed to a foreign (nonself) molecule, cell, or tissue (for example, infective, allogenic, or xenogenic).
  "Similarity profiles between helper T cell epitopes (of self or microbial antigens and allergens) and human or microbial SWISSPROT collections were produced. For each antigen, both collections yielded largely overlapping profiles, demonstrating that self-nonself discrimination does not rely on qualitative features that distinguish human from microbial peptides. [...] Epitopes (on self and nonself antigens) can cross-stimulate T cells at increasing potency as their similarity with nonself augments."

verb

• (botany) To fertilize by the same individual; to self-fertilize or self-pollinate.
• (botany) To fertilize by the same strain; to inbreed.

adj

• (obsolete) Same, identical.
  "I owe you much, and, like a wilful youth / That which I owe is lost; but if you please / To shoot another arrow that self way / Which you did shoot the first, I do not doubt, / As I will watch the aim, or to find both, / Or bring your latter hazard back again, / And thankfully rest debtor for the first."
• (obsolete) Belonging to oneself; own.
• (molecular biology, immunology) Of or relating to any molecule, cell, or tissue of an organism's own (belonging to the self), as opposed to a foreign (nonself) molecule, cell, or tissue (for example, infective, allogenic, or xenogenic).
  "Similarity profiles between helper T cell epitopes (of self or microbial antigens and allergens) and human or microbial SWISSPROT collections were produced. For each antigen, both collections yielded largely overlapping profiles, demonstrating that self-nonself discrimination does not rely on qualitative features that distinguish human from microbial peptides. However, epitopes whose probability of mimicry with self or nonself prevails are, respectively, tolerated or immunodominant and coexist within the same (auto-)antigen regardless of its self/nonself nature. Epitopes (on self and nonself antigens) can cross-stimulate T cells at increasing potency as their similarity with nonself augments."