Definitions of semi

1. Half; partly; as, semiannual; semicircle.

2. a truck consisting of a tractor and trailer together

3. A prefix signifying half, and sometimes partly or imperfectly; as, semiannual, half yearly; semitransparent, imperfectly transparent.

4. Prefix denoting half.

5. A common prefix, signifying half; half of; in part; partially; the compounds of semi are for the most part easily understood, if the meaning of the latter part is known; a hyphen is usually placed after semi.

6. A Latin prefix, signifying half.