n. A kind of latch whose bolt may be locked by a detent so that it can not be opened from the inside by the handle, or from the outside by the latch key.
the GNU version of the Collaborative International Dictionary of English
n. A kind of latch whose bolt may be so locked by a detent that it can not be opened from the inside by the handle, or from the outside by the latch key.
The Century Dictionary and Cyclopedia
n. A latch which is held in its place by a catch, or of which the bolt may be so locked by a detent that it cannot be raised by the latch-key from the outside, nor by the handle from within.
Word Usage
"After locking Callard's apartment with the key so as to engage the deadlatch, he went down the back stairs and out by the alley door."