A person who supports or advocates for the annexation of territory, particularly someone who believes a nation should expand by absorbing neighboring lands.
From annexation plus the suffix '-ist' meaning one who practices or believes in, with roots in Latin 'annectere' (to bind to).
The 'annexationists' in 19th-century America pushed for westward expansion so aggressively that their ideology became known as 'Manifest Destiny'—they truly believed it was America's destiny to span the continent.
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