てっきり

What it means

What does てっきり mean? It means that the speaker believed something to be true with strong certainty, often to be proven wrong later, expressing a sense of surprise or disappointment when the expectation did not come true.

Main meanings

• Expresses a strong, often mistaken belief about a situation that later proves false.
• Tends to accompany a following clause describing what was believed, highlighting the speaker's surprise.
• Widely used in casual speech and storytelling to recount past misunderstandings.

How to use it

Used in casual conversation to recount a past mistaken assumption; followed by a plain-form clause describing what was believed; usually appears in past tense to reflect that the assumption occurred in the past and is not common in formal writing.