Step 1: Define the target word Vast.
"Vast" means extremely large in size, area, or quantity - think of a vast ocean or a vast desert; it always implies something of enormous, immeasurable scale.
Step 2: Eliminate antonyms from the options.
"Tiny" means very small (direct opposite); "Narrow" means not wide (opposite in breadth); "Short" means not long or tall (opposite in dimension); all three are antonyms of vast.
Step 3: Confirm the synonym.
"Huge" also means extremely large in size - it is the closest synonym to "Vast" among the given options.
\[ \boxed{\text{Huge}} \]