Hand waving

From Fresh Dictionary

English

Noun phrase

hand waving, hand-waving

1. ((idiomatic{{#if:|, {{{2}}}{{#if:|, {{{3}}}{{#if:|, {{{4}}}{{#if:|, {{{5}}}{{#if:|, {{{6}}}{{#if:|, {{{7}}}{{#if:|, {{{8}}}{{#if:|, {{{9}}}}}}}}}}}}}}}}}}})) approximation, vagueness, educated guessing, or the attempt to explain or excuse vagaries.

   The sales pitch sounded good, but they did a lot of hand-waving about the price.