A hidden or secret intention; an ulterior motive—an intention not openly shown, often involving personal calculation or desire.
彼女に親切にしたのは下心があるからだと噂された。
There were rumors that his kindness toward her had an ulterior motive.
下心を隠して仕事を進めるのは信頼を損なうことがある。
Hiding an ulterior motive while carrying out work can sometimes damage trust.
恋愛において下心が見え隠れすると相手に不快感を与えることが多い。
In romance, when ulterior motives are visible, they often make the other person uncomfortable.
In kanji classification, the term can refer to forms where the 'heart' (心) component appears at the bottom of a character (a notation used in character analysis).
『思』や『念』のように心が下に来る字形を下心と呼ぶことがある（注記的用法）。
Characters where the 'heart' component appears at the bottom, like 思 or 念, are sometimes referred to as 下心 (notational usage).