1. North America buildings 2-family dwelling: a house that is divided into two halves and is inhabited by two separate families or tenants with separate entrances
2. electronics transmission in both directions: transmission of signals along a communications channel in both directions at the same time, e.g. over a telephone line
1. twofold: consisting of two parts, especially two identical or equivalent parts
2. engineering having two parts performing one operation: consisting of pairs of units or components that perform the same machine function but operate independently
