Telling p. pr. & vb. n. : of Tell

Telling a. : Operating with great effect; effective; as, a telling speech.

Example:
Telling the difference between metric and imperial bolt threads by eye?

Taxonomy
dictionary, Encyclopedia, narration, telltale, thesaurus browser, online dictionary, synonyms, antonyms, incident, law, Translations, Free Online Dictionary, striking effect, smile, speech act, the telling, English dictionary, relation.

Defination from the web:
telling in the Online Dictionary. Meaning of telling. Pronunciation of telling. Translations of telling. telling synonyms, telling antonyms. ... telling - an act of narration; "he was the hero according to his own relation"; "his endless recounting of the ... telling ...