Used informally as a standalone noun meaning "femtosecond" or "femtocell".
Definitionen
A femtosecond; one quadrillionth (10⁻¹⁵) of a second. The laser emits pulses of about 100 femto each.
A femtocell, a small low-power cellular base station used to improve indoor coverage. We installed a femto in the office to boost the signal.