Terrific means very good indeed, or very great in degree. A terrific film, a terrific noise, absolutely terrific.
The reversal is the interesting part: it originally meant terrifying, and the sense of excellent came by way of very great — a terrific noise still keeps the old size without the fear. Terrible and terrific come from the same root and have gone opposite ways. Note terrify, terror, from the same Latin.
1adjectiveterrificVery good indeed.
“You did a terrific job on the garden, and now the neighbours all want your help.”
2adjectivegreatVery great in degree.
“There was a terrific crash as the tree fell onto the car.”
Too few real examples of this word to estimate which sense is commonest.
terrific is a quality of greatness.
Latin terrificus means causing terror, from terrere, to frighten. Terror, terrible and deter come from the same fright.
French
terrifique
English, today
terrific
Built from
From French terrifique. From French terrifique, and its source, Latin terrificus (“terrifying”), from terreō (“to frighten, terrify”) + -ficus, related to faciō (“to make”). by surface analysis, terrify + -ic. The sense of excellent or amazing is an from the original sense of terrifying. Compare similar semantic development in sick and wicked.
Etymology from Wiktionary, CC BY-SA