Definition of "burthensome"

All ye that, as I do, have felt this smart, Ye know how burthensome 'tis at my heart.

1662, J.T., “Grim the Collier of Croyden”, in A Select Collection of Old English Plays, Vol. VIII (4th edition)‎

"I can, madam, but I do not love one," said Anne, thinking of her most burthensome one.

1889, Charlotte M. Yonge, A Reputed Changeling‎

A labour-rent thus became more difficult to enforce, while the increase of wealth among the tenantry and the rise of a new spirit of independence made it more burthensome to those who rendered it.

1890, John Richard Green, History of the English People, Volume I (of 8)‎