noun
conversing in a foreign language while eating
Dated colloquial term, often used among Japanese businessmen to describe the practice of speaking a foreign language (typically English) during a meal, especially in a business context.
昔の商社マンは、海外出張でよく横メシを強いられたらしい。
It seems that old-time trading company employees were often forced to converse in a foreign language while eating during overseas business trips.
noun
Western dish; Western food
Dated colloquial term for Western-style food, as opposed to Japanese cuisine. The 横 (side, horizontal) implies something foreign or non-traditional.
今日のランチは横メシにしようか。
Shall we have Western food for lunch today?
Compound of 横 (side, horizontal, implying 'foreign' or 'non-traditional') and メシ (meal, food). The exact origin is uncertain, but it likely arose in business circles as a playful or insider term.