Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
circum -stīpo or circum stīpo, āvi, ātum, 1, v. a., to surround, accompany, attend (in post-Aug. poetry and rare).
Absol.: magnā circumstipante catervā, Sil. 10, 453.
Pass., Claud. Laud. Stil. 2, 356; id. VI. Cons. Hon. 595.