hand waving


noun

insubstantial words, arguments, gestures, or actions used in an attempt to explain or persuade.

Also hand-wav·ing, hand·wav·ing [hand-wey-ving] /ˈhændˌweɪ vɪŋ/.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019