Furthest toward the east; most easterly in position or location.
From 'eastern' plus '-most' (superlative suffix). The standard modern form for the most easterly position, used since at least the 16th century.
'Easternmost' is the most efficient superlative form—by using '-ernmost' directly on 'east,' English avoided the awkward 'eastermost,' showing how languages optimize for easy pronunciation.
Complete word intelligence in one call. Free tier — 50 lookups/day.