Translation guide
The English phrase 'be dull' can describe a lack of sharpness (literal or figurative), a lack of excitement, or a lack of intelligence. This guide organizes Japanese expressions by these core meanings, from most common to niche.
Describing a blade, tool, or point that has lost its sharpness.
The most common adjective for 'dull' in the sense of not sharp. Can also be used figuratively for slow-witted or sluggish.
Literally 'the cutting quality is bad'. A natural way to say something doesn't cut well, implying dullness.
このナイフは切れ味が悪い。
This knife is dull (doesn't cut well).
A somewhat old-fashioned or colloquial term for a dull blade, often implying it's useless. Can also mean a lazy person.
この刀はなまくらだ。
This sword is dull.
Describing an event, person, or thing that lacks excitement or interest.
The standard adjective for 'boring' or 'dull'. Used for things that fail to hold interest.
その映画は退屈だった。
The movie was dull.
彼の話は退屈だ。
His stories are dull.
Very common word for 'boring', 'dull', or 'uninteresting'. Slightly more casual than 退屈.
この本はつまらない。
This book is dull.
Literally 'lacks interestingness'. A more analytical way to say something is dull.
彼の講演は面白みがなかった。
His lecture was dull (lacked interest).
Means 'plain', 'simple', or 'subdued'. Can imply dullness in the sense of lacking flashiness or excitement.
彼女の服装は地味だ。
Her clothes are dull (plain).
Describing a person who is not sharp mentally.
The same word as for physical dullness, also commonly used for mental slowness or lack of quick understanding.
彼は頭の回転が鈍い。
He is slow on the uptake (literally: his mental rotation is dull).
私は数字に鈍い。
I'm dull with numbers.
A stronger, more formal word meaning 'stupid' or 'dull-witted'. Often used in writing.
彼は愚鈍な男だ。
He is a dull-witted man.
A colloquial and slightly derogatory term for a slow or dull person, both mentally and physically.
あいつはのろまだ。
That guy is dull/slow.
Describing a surface, color, or light that is not bright or shiny.
Describes colors or surfaces that are dull, faded, or lacking brightness. Often used for paint, metal, or complexion.
くすんだ色の壁
a wall of a dull color
金属がくすんでいる。
The metal is dull (tarnished).
Literally 'lacks luster'. Used for surfaces that should be shiny but aren't.
このテーブルは光沢がない。
This table is dull (has no shine).
Means 'cloudy' or 'foggy', but can describe a dull, hazy surface like a mirror or glass.
曇った鏡
a dull mirror (fogged up)
Describing a dull ache or throbbing pain rather than a sharp one.
The standard medical/descriptive phrase for a dull pain. 鈍い here means 'dull' as opposed to sharp.
腰に鈍い痛みがある。
I have a dull pain in my lower back.
Describes a heavy, oppressive, dull pain. More subjective and emotive.
頭が重苦しく痛む。
My head aches with a dull pain.
Describing a dull, gray, sunless day or mood.
Describes a dull, overcast sky or a heavy, gloomy atmosphere. Very common for weather.
今日はどんよりした天気だ。
The weather is dull today.
Simply means 'cloudy', but can imply a dull, gray sky.
曇った空
a dull (cloudy) sky
鈍い (nibui) is for physical dullness (blades, senses, mind). 退屈 (taikutsu) and つまらない (tsumaranai) are for boredom. 退屈 is slightly more formal, つまらない is more casual and can also mean 'trivial' or 'worthless'.
このナイフは鈍い。
This knife is dull.
この映画は退屈だ。
This movie is dull (boring).
このゲームはつまらない。
This game is dull (boring).
While 鈍い can mean 'slow-witted', it is not used to describe an uninteresting event. Use 退屈 or つまらない for that meaning.