Misspelling of idiosyncratic.

A surname from Japanese.

A student at a military school who is training to be an officer. / (largely historical) A younger or youngest son, who would not inherit as a firstborn son would.

(literally) A firework that has been wet and therefore fails to go off correctly. / (idiomatic, by extension) Anything that doesn’t work properly, or fails to come up to expectations; a dud.