la jeringuilla - syringe
  la jirafa - giraffe
  el karateka, la karateka - karate expert, someone who practices...
  Jehová, el Jehová - Jehovah or Yahweh (name of God often...
  la ictericia - jaundice
  el iceberg - iceberg
  integral - complete, comprehensive, total, made...
  el invierno - winter, rainy season (in the tropics)
  el interlineado - space between lines of text, leading
  interino - temporary, interim, stopgap, stand-in
  el IVA (impuesto sobre el valor añadido) - VAT (value-added tax)
  el islote - small island, usually rocky and...
  iracundo - angry, irate, irascible
  intratable - difficult to get along with,...
  la intriga - intrigue, suspense, curiosity, a...
  igualado - level, at the same level, leveled...
  el ideario - ideology, philosophy or approach to...
  ileso - unhurt, unharmed
  irrebatible - indisputable, irrefutable
  inviable - impractical, not feasible, unviable