Verb. Sekkieren means to bother, pester or annoy someone. The person who is doing the irritating thing is being sekkant. The word sekkieren originates from the Italian seccare (to dry out, to dehydrate), which is in turn derived from the Latin siccus (dry). So the implication is that you are desiccating someone, making them itchy and irritable like dry skin with literally “withering” remarks.
Achtung: while there are many things in Viennese life that can be exasperating – like Kurzparkzonen, Meldezetteln or Parteienverkehr hours at the Magistrat – sekkieren is generally done by a person.
The underlying intention makes no difference, whether it is to get you to do something – like take out the trash, give someone a raise or donate to charity – being a pain for the fun of it or even just trying your patience on principle, as a nagging mother-in-law or demanding boss would.
Either way you are being sekkiert, and are well within your rights to be grantig (grumpy).