An advanced square which cannot be attacked by a hostile piece of inferior rank. Foreposts are ideal squares for attacking knights as they have a short range. An absolute forepost is where the position is unassailable. A contingent forepost can only be attacked at the cost of creating a weakness elsewhere.
FOREPOST
Meaning of FOREPOST in English
English glossary of chess terms. Английский глоссарий шахматных терминов. 2012