The þ, or thorn, is an Icelandic letter representing the voiceless dental fricative, which can best be described as the "th-" sound in words like "thing" or "thigh." They have another letter used for the "th-" sound heard in English words like "thy" and "that"; it's called the eth and looks like this: Ð or ð.Þórdís would be pronounced THOR-dees.
Þórdís would be pronounced THOR-dees.