at a loss for words; unable to express oneself adequately
Describes a state where one's feelings or intentions are too strong or complex to be put into words, resulting in insufficient or clumsy expression. Often used when emotions overwhelm the ability to speak clearly.
My gratitude was so strong that I was at a loss for words.
He was so nervous that he could only give a clumsy, inadequate reply.
言葉に詰まる focuses on being stuck and unable to continue speaking, while 意余って言葉足らず emphasizes that the speaker's feelings exceed their verbal ability, leading to insufficient expression.
口下手 describes a general lack of speaking skill or inarticulateness as a trait, whereas 意余って言葉足らず is a situational phrase for when strong emotions cause a failure to express oneself adequately.
A set phrase combining 意 (heart, mind, intention), 余る (to be in excess), 言葉 (words), and 足らず (insufficient). The literal meaning is 'intention exceeds, words are insufficient,' describing a mismatch between one's feelings and verbal expression.