Definition of "buttressed"

[…] St. Bede's at this period of its history was perhaps the poorest and most miserable parish in the East End of London. Close-packed, crushed by the buttressed height of the railway viaduct, rendered airless by huge walls of factories, it at once banished lively interest from a stranger's mind and left only a dull oppression of the spirit.

1918, W[illiam] B[abington] Maxwell, chapter VII, in The Mirror and the Lamp, Indianapolis, Ind.: The Bobbs-Merrill Company