The term HIGH can be broken down into two crossword solutions: ACRO and ALTI. ACRO is a 4-letter prefix meaning 'HIGH, tall, or lofty, ' while ALTI is also a 4-letter prefix meaning 'HIGH in altitude.' Both terms are derived from the Latin word altus, which means 'HIGH' or 'DEEP.' The prefixes ACRO and ALTI are commonly used in scientific and technical contexts to refer to something that is HIGH in altitude or height.