Unnatural or artificial; awkward or forced in appearance or behavior, causing a sense of oddness.
彼の返答はあまりにも不自然で、何か隠しているように見えた。
His reply was so unnatural that it seemed like he was hiding something.
写真の合成が不自然に見える部分がある。
There are parts of the photo editing that look unnatural.
会話が不自然なら、率直に聞き返したほうがいい。
If the conversation feels unnatural, it's better to ask directly.