1. (

• shell ,
• case ,
• casing ,

) the housing or outer covering of something; "the clock has a walnut case" ;

2. (

• casing ,

) the outermost covering of a pneumatic tire ;

3. (

• casing ,
• case ,

) the enclosing frame around a door or window opening; "the casings had rotted away and had to be replaced" ;