Cell-wall destruction initiated by multiple phage adsorption to individual bacteria.
Alterntative…
Exogenous exposure of bacteria to lysins.
The resulting lysis occurs well prior to lysis as would be induced instead via lysis from within. In either case, lysis from without involves disruption of the bacterial cell wall by enzymes which gain access to it from outside of the bacterium.
The earliest use of this term was based on the first definition – lysis induced by the multiple adsorption by whole virions – whereas the endolysin-associated usage is more recent. Note that not all whole phages, nor all endolysins, are able to lyse target bacteria from without.
This is the definition from Adams (1959), p. 440), "Abortive infection accompanied by prompt lysis of a cell, typically following excessive multiple infection."
Consistent with this idea that lysis from without is a form of abortive infection, a number of authors have speculated that they may be observing lysis from without but with this term seemingly defined solely as bacterial death attained following presumptively high multiplicity phage adsorption, that is, without emphasizing that bacterial lysis must also occur. Lysis profile experiments or other means of detecting lysis can and should be used in such cases to confirm that lysis, in fact, can occur following high multiplicity adsorption by a given phage isolate to a given bacterial strain.
References: Abedon (1994) and Abedon (2011).
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