Delete from table with(snapshot)
This is a table hint that can be used in various statements (SELECT, INSERT, DELETE, UPDATE, MERGE). See the related page at msdn: Table hints and the linked Introduction to Memory-Optimized tables.
For further information about isolation levels, see SET TRANSACTION ISOLATION LEVEL (Transact-SQL).

Syntax
WITH  ( &lt;table_hint&gt; [ [, ]...n ] )  
  
&lt;table_hint&gt; ::=   
[ NOEXPAND ] {   
    INDEX  ( index_value [ ,...n ] )   
  | INDEX =  ( index_value )      
  | FORCESEEK [( index_value ( index_column_name  [ ,... ] ) ) ]  
  | FORCESCAN  
  ...
  | SNAPSHOT
  ...

...
SNAPSHOT
Applies to: SQL Server 2014 through SQL Server 2016.
The memory-optimized table is accessed under SNAPSHOT isolation.
SNAPSHOT can only be used with memory-optimized tables (not with disk-based tables).
For more information, see Introduction to Memory-Optimized Tables.