I believe they mean that the random variables have a common support. For example, if X ~ Unif[0,2] and Y ~ Unif[1,3], then their respective PDF's overlap in the interval [1,2], meaning the only interval where both X and Y can have common values is [1,2]. To illustrate, below is a representation of the supports of X and Y, below which is a representation of the real line.
1 Thyroid cancer is a malignant tumor of the thyroid gland. 2  Symptoms of thyroid cancer include swelling in the neck (goiter), neck pain, hoarseness, swallowing and breathing problem, swollen lymph gland in the neck.
WebMD Symptom Checker. Enlarged or swollen glands, Fever, Headache and Stiff neck. WebMD Symptom Checker helps you find the most common medical conditions indicated by the symptoms enlarged or swollen glands, fever, headache and stiff neck including Mononucleosis, Viral pharyngitis, and Acute sinusitis.